Creatures include all animal life that a character might interact with, The characters themselves are, in fact, creatures as well. Not all creatures are identical, but there are some generalities that are common to all creatures, including size, movement, and ways of defending themselves.

To make it easy, we’re going to subdivide creatures into eight categories of size.

When it comes to determining a size, weight is often a better deciding factor than length or height. That’s why gorillas are large and dwarves, like the sturdy ones one might picture from Tokien’s Middle-earth, are medium, even though their heights might not normally indicate such.

A creature has hit points related to their size. (That’s why we care about size above.) Unlike many RPGs, hit points don't increase based on some nebulous level or hit dice. It's purely related to size. Certain skills can potentially increase hit points temporarily or even permanently, but this is not done as part of any sort of natural progression.

We’re going to treat movement speed in a very generic way categorizing creatures as slow, average, fast, and very fast comparative to the category of movement. The three primary categories of movement are running, flying, and swimming. (It should be noted that these aren’t the only ways of travel, and GMs are welcome to add climbing, digging, brachiating, or any other modes of movement they feel are necessary to their campaign.)

As mentioned previously, these speeds are comparative within a certain category of movement, not outside of it. That means that this isn't some general movement speed so much as how quickly they move using a certain mode of movement compared to others who also move in that manner. Outside of that category of movement, it should generally be noted that fast swimmers generally are too slow to catch slow runners and fast runners are generally too slow to catch slow fliers.

Although general categorizations are generally all that's necessary, it's occasionally required to increase granularity beyond a simple average or very fast. When granularity is important, these are reflected by adding a number after the speed initials, e.g. S3 or VF2. Each speed has five possibilities ranging from n0 - n4 (with the 0 generally being left off unless it's needed for clarification). An increase of movement to an n5 would move a race to the next highest division, from slow to average or from fast to very fast,

When does granularity become important? If one creature were trying to catch another creature, the nuanced numbers could be important. Defensive dice determinations could also require knowing granularity nuances.

Any creature can move to the next highest degree (e.g. from S2 to S3 or from VF to VF1) for a short period of time (a few minutes, depending on endurance and other factors). To maintain that level, a creature would have to roll skill checks against their Endurance skill.

Bipedal creatures generally run slower than quadrupedal creatures. Smaller creatures generally run slower (i.e. cover less distance) than larger creatures, though weight begins to become a factor with extremely large creatures. Creatures with flippers and fins almost always move quicker than those without. When it comes to swimming and flying, there is a point where size means more resistance, so the largest creatures often can't move as quickly as those of small or medium size, though the tiniest creatures also have a hard time keeping up. If not otherwise listed, the following table gives a general idea of how one might determine speeds though these are only generalizations and outliers abound.

In nature, smaller creatures are generally harder to notice, harder to hit, and/or reproduce at a larger rate than larger creatures. If not, they wouldn't exist anymore. Although DiceMob doesn't try to account for reproduction rates, it does try to account for the other two methods of smaller creatures protecting themselves. It does so either through additional actions or skills or through additional defense dice, each of which is treated in more detail below.

Any creature of size small or smaller is awarded either an extra defensive action or a defensive skill. (Defensive skills often includes something like camouflage, but it could also include resistances to various attack forms or defensive maneuvers like blocking attacks or dodging them.)

Tiny creatures are awarded an additional defensive action (in addition to whatever was chosen previously for being small or smaller).

Defenders gain additional defensive dice based on their size and movement speed compared to that of their attacker. There's a reason why the phrase “can't hit the broad side of a barn” is a phrase. Because it's large, the broad side of a barn is hard to miss. When attacking, a creatures is generally considered to be attacking a creature generally the same size as it is or larger. When creatures start attacking creatures much smaller than they are, difficulties tend to arise.

Small creatures are much harder to hit, and they become even harder to hit the faster they are. To account for this, one defensive die is awarded for every size smaller a defender is than the attacker, starting with two sizes smaller. (If a defender is two sizes smaller, one die, three sizes smaller, two dice, etc, up to a maximum of six dice for a tiny creature defending against a gargantuan one).

Additionally, if the creature is ALSO a full degree faster based on movement speed (i.e. slow vs average, average vs fast, fast vs very fast) and is moving at full speed or near full speed, that creature is given an ADDITIONAL two defensive dice per degree faster to account for how much more difficult it is to hit a creature that is both smaller AND faster. This would NOT apply if they are engaged in melee combat unless they are employing some form of darting in, attacking, and darting away to take advantage of their movement speed.

In addition to the above defensive dice awarded, flying creatures at least two sizes smaller also gain an additional two defensive dice versus land- or water-bound creatures when that creature is trying to use a touch or melee attack against them, assuming they can reach them at all. Ranged attacks are not so penalized; they are considered flying attacks and they generally move faster than very fast flying creatures anyway.

Note: These additional defensive dice only apply for trying to hit small creatures with something relatively small. Area of effect attacks like an exploding fireball, a cloud of poisonous gas, or a fist the size of a house would not be so penalized because they hit everything within their area of effect, unless the creature could reasonably be considered to escape from that area of effect before the attack came. Likewise cognitive and emotional attacks are not penalized because of size because body size has nothing to do with mental attacks.

For lack of a better term, animal hide is the natural outer covering of creatures built to withstand the elements or attacks by predators. This generally affects non-humanoid creatures though some humanoid creatures might also have tougher or more element resistant hides as well.