A number of rules that define how monsters work in the Worlds of Adventure campaign are different from Pathfinder.

Monster types and subtypes

In Pathfinder and similar game systems, each creature belongs to one of several exclusive types; a creature's type determines certain of its traits and abilities. In the Worlds of Adventure campaign, this is not the case.

In Worlds of Adventure, creatures simply have the traits that they have. Similar creatures have similar traits, and a particular category of creatures (such as "tanar'ri demons") may share many traits, but exceptions may occur, and categories may overlap.

Most creatures fall into one or more categories (also known as "types", "descriptors", etc.), such as "dragon", "humanoid", "fire creature", "living creature", and so forth. A creature may belong to any combination of categories that applies (though some categories may be incompatible, such as "living creature" and "undead creature"). Much like spell descriptors, these categories usually have no intrinsic game effect, but affect how various spells and abilities interact with different sorts of creatures: a ranger's favored enemy ability, the effects of positive and negative energy, the charm person spell, etc.

Big and little creatures in combat

The rules that govern how creatures of different sizes interact in combat are somewhat different in the Worlds of Adventure campaign.

Size modifiers for combat maneuvers

A creature larger or smaller than Medium applies a special modifier to its combat maneuver attack rolls and combat maneuver defense. See the Combat Maneuver? page for details.

Short steps

Just as characters of the common races can take a 5-foot step in any round when they haven't otherwise moved, so larger creatures can take larger steps; this is called "taking a short step" in the general case. A Small, Medium, or Large creature moves 5 feet when taking a short step; a Huge or Gargantuan creature moves 10 feet; a Colossal creature moves 15 feet. Tiny and smaller creatures cannot move even 5 feet with a short step, and must take a move action to move 5 feet or more.

Combat reactions for monsters

Most creatures can make combat reactions to dodge attacks, but not to block. A creature treats its hit dice as its warrior level for the purpose of determining its dodge value.

Some creatures (those that are proficient with weapons and armor, and have a "martial" orientation, such as hobgoblins or fire giants) can block attacks. Other creatures (those whose abilities are focused entirely on things other than martial combat, such as spell weavers) can neither dodge nor block. (Such creatures may be able to take the Dodge feat to gain the ability to dodge attacks.)

See Combat Reactions? for more information on dodging and blocking.

Critical hits

Some types of creatures in the Worlds of Adventure campaign do not take extra damage from critical hits (nor, by extension, from abilities like a rogue's sudden strike, the Deadly Stroke feat, and other abilities which use critical hit mechanics). Magic abilites which activate on critical hits still work against such creatures, if the ability does not depend on the creature having a differentiable anatomy, weak spots, etc.

Creatures are most commonly immune to the extra damage from critical hits due to having a body which is an undifferentiated mass of matter, or due to not having a physical body at all. The most commonly encountered kinds of creatures that fall into this category are:

This is not an exclusive list. In general, a monster which has no part which is any more important to its functioning than any other part is immune to the extra damage from a critical hit.

Monsters with class levels

Some monsters may have "class levels", granting them abilities very much like those gained by characters who are members of character classes. This may come about in various ways: some monsters may study, train, and practice various skills and abilities much like a character of the common races might; other monsters may have the abilities associated with this or that character class simply by virtue of their nature.

Monsters with class levels do not, by default, gain hit dice or level-dependent benefits (base attack bonus, save bonuses, skills, and so forth) from class levels. Thus a storm giant who has the abilities of a 10th-level barbarian still has the same basic statistics and combat numbers as a normal storm giant — but has the ability to enter a rage; a dragon with levels in the cleric class can cast spells and turn undead, but has as many hit points, etc., as a normal dragon of its age; etc. (The exception to this is a monster who gains class levels in excess of its racial hit dice. One way of seeing this is to think of a monster as having its race as its primary class progression, and any class levels it might take as a secondary progression.) Some monsters may even have some, but not all, of the class abilities of one or more character classes (this is often the case for those monsters that gain character class abilities by virtue of their nature, instead of through specific personal experience or training).

Damage reduction

Challenge rating

There is no concept of a creature's "challenge rating" in the Worlds of Adventure campaign.

The difficulty of defeating a monster varies with so many variables — party size and composition, various character build choices made by the players, environment, etc. — that assigning a number to the "level of challenge" presented by the creature is somewhere between impossible and useless. In addition, many monsters may have strengths and weaknesses that are not "balanced" with each other, because monsters are not "designed to be encountered at a certain level". For that matter, many "monsters" may be more effectively "defeated" via diplomacy, stealth, trickery, indirect combat, or various other approaches that don't involve directly engaging with the creature's combat capabilities.

Thus, and because nothing in the game formally depends on how difficult a creature is to defeat, creatures are not assigned "challenge ratings" in Worlds of Adventure. (In the absence of CR, a good rough estimate of a creature's general "power level" is its hit dice or level.)