This article looks at twenty-seven of the more problematic rules found in first edition Advanced Dungeons & Dragons.
By R. Nelson Bailey
First edition Advanced Dungeons & Dragons is a wondrous game that has left an indelible imprint on those that have played it — this author included. However, its quirky and idiosyncratic rulebooks can be difficult to navigate even for veteran players. Difficult editing problems endemic to these books heap confusion on the reader leaving them wondering what exactly some of the rules mean. Typical problems arise from vague wording, omissions, typos, inconsistencies, contradictions, and rules spread out over different sections of a book or multiple books. Another issue is that some later published books and articles add, expand, or clarify rules found in the older books. Furthermore, with differing rules from multiple editions of D&D and the use of house rules in many campaigns, the confusion is multiplied tenfold. This article takes a close look at some of the more overlooked and vexing issues in 1st edition AD&D to help Dungeon Masters and players alike attain a better understanding of the game.
5th-Level Cleric Level Title
Glance at the “Clerics Table I” in the Players Handbook (p. 20) and you will notice that a 5th-level cleric has no level title. There is just a blank space. What does this mean? Do 5th-level clerics not have a title? Is it just the same as a 4th-level cleric? Is it a typo? The answer is that it is indeed a typo. The missing level title is actually “Prefect”, as noted on the AD&D Dungeon Masters Screen*. This level title is also noted “prefect” in T1-4 Temple of Elemental Evil (p. 59), and the super-module, GDQ1-7 Queen of the Spiders (p. 14).
* The screen released in 1979 with the Erol Otus cover art, not the revised REF1 from 1985, which does not list it. Note that the missing title on the screen is misspelled as “Perfect”. How perfectly ironic.
A Natural “20” Always Succeeds
With 1st edition AD&D, rolling a natural “20” in combat is not a guaranteed hit like it is in later editions, nor is a natural “1” at complete miss. In some cases, an attack hits only if the die roll, plus any bonuses, is equal to or greater than the target number, which could be a number greater than 20 (Dungeon Masters Guide, p. 82). This makes some targets “hit proof” (DMG,
p. 70). However, this is not the case with saving throws, where a natural “1” always fails (DMG, p. 81), and (optionally) a natural “20” always succeeds.
Carrion Crawler Paralysis
The Monster Manual fails to note the duration of this monster’s paralysis attack. To further complicate matters, there are multiple contradictory official answers. The Advanced Dungeons & Dragons Monster Cards, Set 3, lists the duration as 2d6 turns; T1-4 Temple of Elemental Evil lists it as 1d4+1 turns; and “Dispel Confusion” (Polyhedron, Issue 2, p. 3) notes that it is 5d4 rounds. The latter duration is given by Gary Gygax himself, so that is the most official answer.
Cold Iron
The monster manuals state that bodaks, ghasts, quasits, wolfweres, and demons can be harmed by cold-wrought iron weapons. Once more, the rulebooks neglect to describe these weapons, or explain their properties. “Dispel Confusion” in Polyhedron (Issue #32, p. 29) defines cold-wrought iron as, “iron which is shaped without heat, generally by pounding and filing”. However, weapons created by this process bend and break more easily than forged weapons.
The adjudication of illusion spells in 1st edition AD&D are very loose.
Deadly Illusions
The rules governing the adjudication of illusion spells in 1st edition AD&D are very loose. In fact, they really are rough guidelines with few specific details. Invariably, this leads to a mare’s nest of questions from DMs and players alike such as, “Can an illusion kill a character?” Some would conclude that, “yes, they can”. After all, the vagueness of the rules leaves them open to interpretation. First, let’s clarify exactly which “illusions” we are referring to. In this case, it is the “phantasmal force” family of spells. This group of related spells includes phantasmal force, improved phantasmal force, spectral force, advanced illusion, programmed illusion, and phantasmagoria. It also includes magical devices that create illusions (e.g., wand of illusion, deck of illusions), and monster spell-like abilities, such as illusions created by devils. It does not include illusion-based spells such as phantasmal killer, (demi-) shadow monsters, and (demi-) shadow magic. These open-ended illusions allow their caster to create nearly anything they desire, disappear when struck unless the caster is concentrating on it, and does not affect victims that successfully disbelieve them (see “phantasmal force”, Players Handbook, p. 75). A spellcaster can use these spells to create nearly anything — an avalanche, a fireball, or a hill giant. However, while formidable, these illusions cannot kill their victims. Instead, “slain” victims are put into a “cataleptic state” (BATTLESYSTEM box set, p. 26). Regrettably, the “cataleptic state” is never defined. As noted in Dragon Magazine (Issue #130, p. 23), the rules in the Dungeon Masters Guide concerning unconscious characters (p. 82) fit the best for this condition.
Note: Non-intelligent (0 INT) creatures, such as dinosaurs (WG6 Isle of the Ape, p. 3), and undead are immune to illusions (Fiend Folio, p. 97) .
Demi-Human Base Move
You need to find out how fast your dwarf character moves, so you take a look through the rulebooks. The only place you find any mention of it is in the Monster Manual where it lists a dwarf’s Movement Rate as 6”*. This seems low, but, hey, they do have short legs. However, the Movement Rates listed in this book are not wholly accurate. This is because the demi-human and humanoid statistics shown in the monster manuals are indicative of adult fighting types. Thus, their Armor Class and Movement are reflective of individuals outfitted in armor. In the case of dwarves and gnomes, chain mail is their armor of choice**. Thus, their Movement Rate in this book is adjusted lower according to the bulkiness of the armor worn (see Dungeon Masters Guide, p. 27). In most instances the actual base Movement of demi-humans and humanoids should be higher (along with their Armor Classes). Unfortunately, no rule book lists these rates. An unofficial list did appear in Polyhedron (Issue #25, p. 28) that appears quite satisfactory. It lists their Movement Rates as follows: dwarf 9”; elf 12”; gnome 9”; halfling 9”; half-elf 12”; half-orc 12”; human 12”.
* Other demi-human listed here are: elves as 12”; gnomes 6”; halflings 9”; and humans 12”.
** Oddly enough, elves wear chain mail, too, though the MM lists their Movement as 12” instead of the adjusted 9”. Possibly an editorial oversight.
Dragon Breath Damage
This topic has often been source of much confusion in the 1st edition AD&D game. The misunderstanding comes from an ambiguous sentence located on p. 30 of the Monster Manual. It reads: “The breath weapon causes damage equal to the dragon's hit points”. Does this mean that the damage inflicted is equal to the dragon’s maximum hit points? Or, that it is the dragon’s current hit points, like how it is done in the “Basic” D&D game? However, the issue is made clearer under the ”Example of Subduing a Dragon” heading on the same page. There, a party of adventurers inflicts 44 hp of damage on an 88 hp red dragon in the first round of combat. On the second round the dragon breaths inflicting 88 hp of damage. From this example, it is plain that dragon breath inflicts the dragon’s maximum hit points in damage*. Furthermore, this method is confirmed by “Dispel Confusion” (Polyhedron, Issue #5, p. 10).
While we are on the subject of dragons, do the breath weapons of Good-aligned dragons that have additional effects, such as sleep, slow, or repulsion, cause damage in addition to those effects? These breath weapons all have secondary, non-lethal effects. As such, causing damage to a target makes little sense if the goal is not to kill them. Once again, this is never specifically addressed in the Monster Manual or any other rulebook**. In 2nd edition AD&D, however, these types of breath weapons do not inflict damage, they only cause the magical effects (see the “metallic dragon” entries in the AD&D Monstrous Manual).
*One might say that the example is not a true one since the adventurers are attempting to subdue a dragon. However, the rules presented in the Unearthed Arcana (p. 109) gives no indication that subdual in any way reduces damage inflicted by the victim.
** The pre-AD&D tournament adventure, The Lost Caverns of Tsojconth (the precursor to module S4), mentions that the breath weapons a copper and a bronze dragon do inflict damage. Conversely, the module, The Ruins of Adventure (p. 5), notes that the damage from the lightning breath weapon of the bronze dragon, Srossar, inflicts damage equal to its "current hit point". It does not mention anything about damage from its repulsion breath weapon. Note the error with the lightning breath weapon, which is incorrect.
Exceptional Strength
The Players Handbook (p. 9) is clear that fighters are the only class to possess exceptional (or percentile) Strength. Is this really the case? The problem, once again, is that the wording in this section is misleading. The text explicitly says “fighters” with no mention of the fighter sub-classes, i.e., the paladin and ranger. Does this mean that the fighter sub-classes are not allowed to have exceptional Strength? Despite what the text says, the answer is, yes, these classes are entitled to it. Broadly speaking, this is because paladins* and rangers are fighters, just as illusionists are magic-users, druids are clerics, etc. (Polyhedron, Issue #22, p. 25). As such, sub-classes are entitled to all the basic abilities of their main class unless the class description text states otherwise. You can see an example of this with the “Hit Point Adjustment” section under the description of Constitution ability (PHB, p. 12). Here, it states the higher hit point adjustment numbers for a 17 or 18 CON applies to fighters “including the fighter sub-classes paladins and rangers”. This is the rationale, which one might say is a circumstantial, not definitive, answer. However, a conclusive answer is found in Unearthed Arcana (p. 8) where a cleric/ranger is noted to have exceptional Strength. Furthermore, The Rogues Gallery (pp. 23-25) also lists several paladins and rangers with exceptional Strength scores.
*Yes, the Unearthed Arcana changed the paladin to a sub-class of the cavalier, but there is no sense belaboring the point.
Falling Damage
Falling damage in most editions, including 1st edition AD&D, is 1d6 for each 10’ fallen up to a maximum of 20d6. It says so right there on p. 105 of the Players Handbook. No issues here, let’s move on. Well…not so fast. Yes, it does unequivocally say that, and that is how most everyone has played it for over the last five decades. However, the rule was officially altered by Gary Gygax five years after the publication of the PHB. It seems that GG noticed that his original notes about falling damage were incorrectly edited (Dragon Magazine, Issue #70, p. 13). The actual text should have read, “1d6 per 10’ fallen, cumulative…the damage mounts geometrically: 2d6 for the second 10 feet fallen, 3d6 for the third 10 feet, etc…” (Dragon Magazine, Issue #69, p. 21). This revised rule was later included in the Dungeoneers Survival Guide (p. 19).
Ghoul & Ghast Paralysis
Like the carrion crawler, the Monster Manual gives no duration for this ability. Again, there are many conflicting official answers. You can read my in-depth discussion on the topic here. If I had to choose a single answer, it would be 5d4 rounds, same as the carrion crawler (see above).
Helmet Use
An often-overlooked rule in 1st edition AD&D concerns the consequences of not wearing a helmet. Any time a helmet-less character is attacked, a d6 is rolled. If the die roll is a “1”, the character is struck in the head, which is considered to have Armor Class 10 (Dungeon Masters Guide, p. 26). While this rule makes sense, I have never used it, nor have I ever met anyone that has. This would require a roll of a d6 along with a d20 each time a character without a helmet is attacked. Furthermore, the DM would have to do this for all melee attacks versus magic-users and monks, since both of these classes cannot wear armor. (Helmets would be considered armor since they are listed under the “Armor” heading on the PHB equipment lists). Note: The text in the DMG states that a great helm gives the wearer’s head “AC 1”. However, AD&D Dungeon Masters Adventure Log (p. 1) says that use of a great helm gives a –1 (bonus) Armor Class modifier to the head only.
Item Saving Throws
Fireballs, dragon breath, disintegration, falling off a cliff, or the electrical blast of a glyph of warding. When characters are struck by destructive attack forms such as these, any items on their persons must also save or be destroyed. These rules are detailed on pp. 80-81 of the Dungeon Masters Guide. It is surprising how few DMs use this rule. Possibly it is because they cannot endure the howls of disbelief from stunned players as their favorite magic items are burned, smashed, and shattered. Like I have always said, “Players would rather have their characters die than to lose all their stuff”. Second edition AD&D (DMG, p. 58) adds a caveat not present in 1st editionAD&D that carries items save only when the character fails their saving throw versus an attack form.
Level Limits for Player Characters
First edition AD&D places restrictions on the highest level a demi-human character can achieve*. Human characters, however, have no such limits; they can attain an unlimited number of levels in any class (Players Handbook, p. 14). Since the goal of the game is to increase in level and power, why must demi-humans abide by these seemingly arbitrary limitations? The main reason is for game balance. These races possess a number of abilities (e.g., special vision and detections, saving throw bonuses, multi-classing, etc.) that give them a distinct advantage over humans, especially at lower levels. (See Players Handbook, p. 6; Dragon Magazine, Issue #16, p. 16; Polyhedron, Issue #13, p. 5.) Few players would opt to play a human character should no such incentive exist. Another reason is that Dungeons & Dragons was envisioned as existing within a humancentric milieu on worlds similar to those depicted in the fantasy tales, folklore, and mythology which the game is based on (Dungeon Masters Guide, p. 21; Dragon Magazine, Issues #16, p. 16, & #95, p. 8). Since the players of the game are human, they relate better with the motivations and sensibilities of humans over non-humans. The game rationalizes a human-dominated world because humans are presumed to be more adaptable than demi-humans and humanoids. This offers them a greater range of possibilities to increase in power (Dragon Magazine, Issue #29, p. 13). Thus, their drive to succeed and inherent potential — for good or bad — is greater despite their apparent handicaps. This explains why a human with a relatively short lifespan can attain greater heights in terms of level potential than can a long-lived elf or dwarf.
* The exceptions being the thief class (for dwarves, elves, gnomes, and half-elves) and assassins (for half-orcs). Keep in mind that the Unearthed Arcana (pp. 8-9) greatly increases the ceiling level for demi-humans based on Prime Requisite ability score. Furthermore, a single-classed demi-human have a maximum level limit of two greater than multi-classed characters (UA, p. 8).
Magic Bows
According to the Dungeon Masters Guide (p. 168), arrows fired from a magic bow have a +1 ‘to hit’ and to damage. However, the text omits whether or not a non-magical arrow fired from a magic bow can strike a monster that is harmed only by magic weapons. To find the answer, one has to look at the text in similar magic items descriptions. In this case, the text for sling of seeking +2 (DMG, p. 169) indicates that missiles fired from this weapon will strike creatures immune to normal weapons. From this example, one can reasonably conclude that this property applies to all magic weapons that fire ammunition. Compare this with “Basic” D&D (Moldvay, Mentzer) which offers no clear answer to this question; the D&D Rules Cyclopedia (p. 243) notes that arrows fired from magical bows are considered magical; while 2nd edition AD&D indicates that they are not.
Magical Aging
The Players Handbook (p. 12) states that petrified or polymorphed characters will die unless they make a successful System Shock Survival roll. However, the text also notes that this roll must be made for magical aging as well. This includes magical aging caused by use of alter reality, gate, limited wish, restoration, resurrection, or wish spells, being the recipient of a haste spell, drinking a potion of speed, or being struck by a staff of withering (Dungeon Masters Guide, p. 13). Aging attacks by monsters, such as ghost or time elemental, do not require the victim to make System Shock Survival roll, as they are not “magical” in nature (see “potion of longevity”, DMG, p. 126). Presumably, this potentially fatal penalty serves as a balance to discourage the overuse of these powerful magics.
The mind flayer’s most feared ability is its mind blast attack.
Mind Blast
The mind flayer’s most feared ability is its mind blast attack. However, the Monster Manual (p. 70) never described exactly what it does, and no other book explains what it is. However, the mind blast is really the psionic attack, psionic blast. To further complicate matters, the MM also incorrectly lists the mind flayer’s psionic attack mode as “B” (i.e., mind thrust), when it should read “A” (i.e., psionic blast). (See Dragon Magazine Issues #43, p. 17, and #70, p. 63, or Polyhedron, Issue #26, p. 23).
Monster Infravision
We all know that many, many monsters live in lightless dungeons or caverns. A common question is, “How do these monsters see in these environments?” The Dungeon Masters Guide (p. 59) give some insight into this issue by noting that, “Most monsters inhabiting underground areas will have this form (i.e., 90’ range) of infravision.” Unfortunately, the wording in this sentence is slightly ambiguous. One can read it two ways. 1) Of underground-dwelling monsters that possess infravision, will they have the 90’ variety? Or, 2) the majority of monsters that live underground will have infravision, which will be in the 90' range? Unfortunately, a definitive official answer clarifying this was never given. However, one can confidently surmise that it is the latter since so few monsters in the manuals are mentioned having any form of infravision. The infra-visual capabilities of only a handful of monsters are listed — mostly humanoids and demi-humans. This was either an oversight, or it was done so as to avoid being repetitive. Note: The Players Handbook (p. 102) mentions that dungeon-dwelling monsters possess 120’ infravision. This contradicts what is stated in the DMG. The latter book, however, should take precedence over the former since it was published at a later date.
Movement in Melee
The rules governing character movement in melee 1st edition AD&D is, to say the least, less than concise. So much so that in many games I’ve personally participated in, melee movement was generally glossed over. As long as a move seemed reasonable, it was alright. For those wishing for more exacting answers, one has to look closely at multiple books. The Players Handbook (p. 102) indicates that creatures can move their base Move Rate in tens of feet during a single combat round. During surprise rounds, however, movement is measured per segment at a rate equal to the base Move in feet (Dungeon Masters Guide, p. 61; PBH, p. 102). Combat movement takes place on step “4.E” of the combat round sequence (DMG, p. 61), after missile discharge, but before melee attacks. By comparison, D&D (Moldvay Basic set, p. B34) allows one to move up to one-third of their Movement rate in melee; and 2nd edition AD&D lets one move their base Move times ten feet in a single round.
Multi-Classed Characters
Determining which strictures a multi-classed character must follow can be frustrating. In most cases, lack of concise wording in the rulebooks regarding specific details is the problem. Listed below are answers to some of the more common issues players have concerning multi-classed characters:
Starting money is equal to all classes of the character combined (Polyhedron, Issue #16, p. 31).
Weapon proficiencies and non-weapon proficiencies for multi-classed characters are cumulative (Polyhedron, Issue #18, p. 29; Dragon Magazine, Issue #139, p. 68).
Rolled hit points are divided between the character’s two or three classes (fractions less than half are rounded down; those greater than half are rounded up) (Players Handbook, p. 19).
Uses the most favorable savings throws of their classes (Dungeon Masters Guide, p. 79).
Experience points are always divided evenly between the classes, even when one or more classes have reached their level limit (Players Handbook, pp. 15-17).
Multi-classed Cleric: Can use edged weapons (c.f., unlike 2nd edition AD&D where they must use blunt-type weapons only, PHB. 62) (Players Handbook, p. 32). Examples of this are found in A1 Slave Pits of the Undercity and C6 The Official RPGA Tournament Handbook.
Multi-classed Fighter: They can have exceptional Strength (Dragon Magazine, Issue #46, p. 56), but cannot use weapon specialization (Dragon Magazine, Issue #103, p. 48).
Multi-classed Magic-user: Can use the weapons and armor of their other classes. As noted in the Players Handbook (pp. 32-33) and Dragon #103 (p. 16), multi-classed magic-user can cast spells while wearing armor (c.f., as they are in 2nd edition AD&D, PHB, p. 62). Other examples of this are noted in A1 Slave Pits of the Undercity, C1 The Hidden Shrine of Tamoachan, G1-2-3 Against the Giants, I2 Tomb of the Lizard King, and S4 The Lost Caverns of Tsjocanth.
Multi-classed Thief: The Players Handbook (p. 18) notes that these characters must abide by the restrictions of the thief class concerning use of weapons and armor. Yet, numerous published examples showing multi-classed thieves using non-thief armor and weapons indicate that this is not the case (e.g., G1-2-3 Against the Giants, D2 Vault of the Drow, I11 Needle,). The exception being multi-classed half-orcs, who must use the least favorable type of armor (PBH, p. 17). Thieving abilities cannot be employed when wearing armor not usable by the thief class, including a shield (Players Handbook, pp. 15-17, & 32-33). The Unearthed Arcana errata from Dragon #103 (p. 16) notes that thieves can use thieving abilities while in non-thief armor types, but with penalties found on the updated THIEVES TABLE II (p. 49). The updated rules from the UA take precedence over the earlier PHB rules. Finally, thieves cannot backstab with weapons, or while wearing armor, not normally usable by their class (Dragon #103, p. 16). Examples of multi-classed thieves wearing other armors are found in A4 In the Dungeons of the Slave Lords and S4 The Lost Caverns of Tsjocanth.
Neutral Clerics & Turning
If you read through the rules detailing turning undead (Dungeon Masters Guide, pp. 65-66 & 75-76), you will notice that Good-aligned clerics “turn” undead, while Evil clerics “command” them. Yet, nothing is ever mentioned about what Neutral clerics do. More specifically, what Lawful Neutral, Chaotic Neutral, and True Neutral* ones do. This oversight has left many puzzled players asking, “Do these clerics turn or command undead?” The short answer is that there is no official answer to this question. First, some might doubt that Neutral clerics are even allowed in the game. However, this notion is dispelled by a section in the Players Handbook (p. 20) that notes that, “clerics can be of any alignment…save (true) neutral”. Furthermore, Neutral clerics must possess the ability to affect undead since they are clerics, and nowhere in the rulebooks does it state, or even intimate, that they cannot. This topic has been covered in a couple places with no satisfactory answer given. “Sage Advice” in Dragon Magazine gave no conclusive answer (Issue #136, p. 52), and “Dispel Confusion” in Polyhedron covered it twice (Issues #8 & #17) offering two differing solutions. However, the definitive answer to this question is given in the “Arcana Update, part 1” article from Dragon #103, p 16. Here, it states that “any non-evil cleric should be treated the same as a good cleric for purposes of determining the success and outcome of attempts to turn undead.” Well, there you go.
The probable reason for this oversight stems from the fact that Neutral clerics did not exist before their introduction in 1st edition AD&D. In the original Dungeons & Dragons game (i.e. the “brown books”), and in AD&D’s prelude, the Holmes “Basic” D&D set, clerics were only of Good or Evil alignment. This meant they either Turn or Command undead. These games used the “Five-Alignment” System, and Lawful Neutral and Chaotic Neutral did not yet fully exist (they were simply called “Lawful” and “Chaotic”, respectively). The AD&D Players Handbook (1978) introduced the more-familiar “Nine-Alignment” System allowing for clerics of these two previously unavailable alignments. Since this appears to be a late addition to the evolving game, most likely the notes on turning that would appear in the DMG were never updated to address Neutral-aligned clerics.
* The Players Handbook (p. 20) notes that clerics can be of any alignment, except True Neutral. Only druids could be that alignment, and they have no ability over undead. However, this was changed in the Unearthed Arcana. As noted on p. 7 of that book, clerics can have "any" alignment, including True Neutral.
Parrying
Another forgotten 1st edition AD&D rule is that one can opt to parry an opponent’s attack. The parrying character loses their attack, but causes their opponent to subtract their Strength ‘to hit’ from their attack roll (Players Handbook, pp. 104-105). You can see why it was forgotten.
Possession
The 1st edition AD&D books contain a number of references to demons and devils having the ability to possess others. The Players Handbook (“exorcise” spell entry, p. 48; “mind bar” psionic ability, p. 115) refers to possession by demons and devils. Two specific references concerning demonic possession occur in Dungeon Masters Guide. Specifically, that the protection from possession scroll prevents possession by a “demon, devil, night hag, or similar creature”. (p. 128); and that the wearer of an amulet of life protection “cannot be possessed by…demonic or diabolic means” (p. 137). The World of Greyhawk box set also gives an example of a “small demon” possessing a dragon. Reading these, one gets the impression that possession is a standard ability of these types of lower planar creatures. The only specific mention of this concerns demon lords and princes using their amulets to magic jar once per day (Monster Manual, p. 16). The rules are inconclusive as to whether or not demons, devils, and related creatures (e.g., daemons, demodands) are able to possess other beings. However, it is in line with the folklore that these monsters are based on, so it is within reason for a DM to include this ability in their campaign. If you do opt to include a broader possession ability, I suggest you treat it as a magic jar spell with more limitations on when it can be used (e.g., one a week, month), and scaled to the Hit Dice and Intelligence of the creature, with weaker ones having less control over their victim and, possibly, saving throw bonuses.
Spellcasting in Armor
An oft-repeated rationale for magic-users not wearing armor is that it spoils their spells. The 2nd edition AD&D Players Handbook (p. 42) even addresses this rumor directly (q.v.). However, this is really a case of misattribution. Wearing metallic armor does spoil the spells of druids (PHB, p. 21). The Players Handbook (p. 25) states that magic-users cannot wear armor and use most weapons because martial training is “foreign to magic-use.” Simple as that. Well…that and game balance…and to keep the roles of the classes separate and distinct.
Spell-like Abilities
These powers resemble spells but without the need for memorization or the process of casting. They include spell-like functions from magical devices, such as from wands (Dungeon Masters Guide, p. 65), and innate spell abilities possessed by monsters, such as demons and devils (DMG, p. 195). They are also referred to as “at will” or “innate” powers. Monster spell-like abilities require no components (i.e., verbal, material, or somatic), and are simply willed into being. Thus, they may be used even while paralyzed or bound, or in total silence (“Dispel Confusion”, Polyhedron, Issue #9, p. 6). Each “at will” ability can be used one at a time, once per round. This is spelled out in the Monster Manual (p. 19): “only one [spell-like ability] may be used at any given time.” Furthermore, monsters cannot make a physical attack and use a spell-like ability in the same round (H4 The Throne of Bloodstone, p. 64). Spell-like abilities require no real effort to initiate having a 1 segment casting time, according to the above-noted “Dispel Confusion”. However, they still function as a spell in regards to when they occur during the combat round sequence (see DMG, p. 61, step “4.D”) as the DMG (p. 65) notes they “occur simultaneously with the discharge of missiles, spell casting, and/or turning undead”.
Don’t let “rules lawyers” sway your better judgment.
"The Spirit of the Game"
Read about Gary Gygax's afterword in the Dungeon Masters Guide here.
Thief Abilities
The thief skills are often a source of confusion. Deciphering exactly how they operate is difficult due to the fact that the rules are spread over multiple sections of text. That, and the usual vague wording that appears in many 1st edition AD&D rulebooks. Let’s take a closer look at a few problematic thief abilities to sort them out.
Backstabbing: Thieves must surprise their opponent to gain a backstab attack (Players Handbook, p. 27). They do this by making a successful move silently roll (PHB, p. 28). Backstabbing does not function if an opponent is aware of the presence of the thief. This means that in most situations they will only get one chance to backstab chance (Dungeon Masters Guide, p. 19). Missile weapons cannot be used to backstab, only melee weapons (PHB, p. 27; Polyhedron, Issue #16, p. 30).
Finding/Removing Traps: This ability only functions with mechanical traps (Players Handbook, p. 27). Magical traps, or those hidden by magical means, cannot be found or removed (Dungeon Masters Guide, p. 19).
Hiding in Shadows & Moving Silently: A thief cannot employ both of these skills in tandem so as to sneak about unseen, as the hiding in shadows only functions when its user remains motionless (Players Handbook, p. 27). Furthermore, hide in shadows fails with opponents that use infravision (PHB, p. 28).
Undead Abilities
Misunderstandings abound regarding the subject of undead creatures. I suggest you read my comprehensive article on the topic. You can link to it here.