Monsters can come in variations and forms unlike the ones listed in the monster books. Variations on monsters are common in modules and other publications throughout the age.

An at-will ability can be used on the same round as an attack routine (e.g. demons). Unless the monster entry provides an exception, a monster can use only one activated at-will ability per round.

Abilities which are triggered by some situation and “passively” activate are not included here; unlimited passive abilities, one at-will ability, and regular attack routine(s) could all be performed on the same round.

These are abilities such as the hell hound's breath and the iron golem's breath, which both use language like “in addition to the regular attack”. These monsters perform their regular attack routine and use their ability on the same round, as with at-will abilities.

Monsters who have abilities such as “once per day” or “three times per week” will typically not have used any of these use when the players first encounter them. This is especially the case when the monster is encountered randomly, such as in a wilderness encounter. If instead the monsters in question are part of a scenario where they are likely fighting other monsters regularly, the DM may assign some chance for one or more uses to have been expended. When in doubt, dice 50-50 chance for each use.

Ghouls, carrion crawlers, and other creatures which paralyze but do not have an effect duration listed paralyze for 1d10+2 turns.¹⁾

Saves are always for breath weapon, even for “poison” breaths like green dragon breath. Bonuses to poison saves do not help against breath weapons.

See Dragon.

See Constriction.

Use rules under Dracolisk MM2 entry to determine if gaze is met, unless otherwise stated. Ranged avoiding-gaze attacks always miss, only melee has a chance to hit while avoiding gaze.

Monsters’ polymorph ability is polymorph self unless explicitly stated otherwise.

Some monsters have more than one listed AC. In some cases, rules are provided in that monster entry to determine which AC is targeted (e.g. die roll, positioning).

In cases when no rules are provided, or when positioning isn't obvious, the same rules for attacking a helmetless character can be used.^Ex2) If the attacker is intelligent and declares that they are targeting a particular body part, they will strike it on a 3-in-6; otherwise the attack strikes the AC least-favorable to the attacker. If the attacker is unintelligent, they will happen to strike a weaker AC location on a 1-in-6. If there are multiple locations with weaker-than-max-AC locations, a random die roll can be made to see which one is hit.

See rules on monster shape change.

Monster abilities all cease functioning after the death of the monster unless the MM states otherwise (e.g. fire beetle glands). This includes rust monster antennae, medusa heads, and ooze acid.³⁾ However, these body parts can be used as material components for magic item fabrication.

Brain moles always mind thrust with 121 strength, and do not have points to spend or lose. The brain mole mind thrust is more of a natural power than the standard psionic mind thrust. They cannot be psionically attacked as a psion, only escaped, slain “normally,” or 100+ point psionic blasted.⁴⁾