Size
Creatures larger or smaller than adult humans get adjustments based on size which can change how creatures interact.
HUMAN-SIZED
Most adult humans are size 6, standing between 125 and 180 cm tall (4'1"-5'10") though a few might be size 5 (80-125 cm, 2'7"-4'0") or 7 (181-245 cm, 5'11"-8'0"). For simplicity's sake, a size 5-7 creature is treated as a 2 x 2 x 2 yard/meter cube but does not have the Blobular shape. Every size lower is roughly half as tall and voluminous while every size larger is roughly 50% bigger than the previous size.
Size2 x 5 = max CM in height for biped or length for quadruped or 3/4 this amount for blobular creatures
Reach
A creature's reach determines how far away they can touch things or hit them with melee attacks. By default, their reach is a number of yards equal to (Dexterity + Size + Wisdom)/10, rounded down. Reach is not always how long a creature's arms are, but also how quickly and accurately they can lunge forward and back.
Speed
A creature's speed is how many yards they can move with a single action. By default, a creature has a land speed equal to their Agility + their Size + their Strength. Some creatures may have other bonuses to this speed or may have burrowing, climbing, flying, gliding, o swimming speeds. When determining if a creature can continue chasing another creature over time, you apply Endurance instead of Size to rolls for chases that take place over extended periods of time (greater than 1 minute).
ACTIONS
If a creature is two sizes larger or smaller than you, you...
- cannot flank them
- cannot gain high ground bonuses against them
- cannot take attacks of opportunity against them
- can move through their space without having to overrun them, treating it as difficult terrain
Creatures with the Blobular shape or Amorphous ability are an exception. They can make attacks of opportunity against creatures of any size smaller and prevent smaller creatures from moving through their space.
CARRYING CAPACITY
A creature can carry an amount of gear weighing up to Strength + Size. An item's weight is equal to its size unless it has the Lightweight or Heavyweight type, in which case it has half or double its size, respectively.
More Legs: Quadrupeds and tauric creatures can carry 50% more than other types of creatures.
Redundancy: Carrying multiple items of the same exact type and size (such as carrying multiple ammo clips, multiple potions, multiple throwing daggers, etc.) counts as only 1 per 3 so long as each of them items are a smaller size than the creature's size.
RAGDOLLING
If you pin a creature that is more than 1 size smaller than you, you can use them as an improvised melee or thrown weapon. The damage dealt is based on the victim's size as an object and the wielder's Strength modifier. The victim and the target share the damage dealt 50/50. A grappled creature or swallowed creature cannot suffer this humiliation, only one that remains pinned.
CLIMBING CREATURES
It’s possible to climb a creature that's two sizes larger than you or larger treating their Parry DC as the Climb DC. If successful, you add your weight to the creature's carrying load and move upwards the appropriate distance. While climbing a creature, you are treated as flanking it for the purposes of weapon attacks you make against it despite the size difference.
MASSIVE
Some colossal creatures and objects have the massive trait. Such creatures are treated as terrain rather than an actual creature by most smaller creatures. They are immune to damage dealt by weapons that are not area of effects. Siege weapons and massive spells are needed to even scratch such behemoths. For simplicity's sake, treat creatures with this trait as if they were one size larger than colossal.
TARGET CREATURES
Spells and other effects that target 2 or more limited number of creatures or objects are assumed to target medium-sized ones unless noted otherwise. If the spell lifts, moves, grants or adjusts base speeds, or transports targets, assume it can include 4 small targets instead of one medium target, 16 tiny per medium, 64 diminutive per medium, and 256 fine per medium. In reverse it can affect 1 large target per 4 medium targets, 1 huge per 16 medium, 1 gargantuan per 64 medium, and 1 colossal per 256 medium. Effects that target "self", "personal", or only 1 creature, have no size limitation. Instead of targeting objects, you can target a single 5-foot space per medium target and affect a wall, ceiling, or floor (if possible).
WEAPON SIZES
Ignore the normal size adjustments for weapon damage dice from the weapons table for small and large weapons and from Improved Natural Attack and similar effects. Weapons designed for Medium and smaller characters deal their normal weapon damage dice as medium creatures. Weapons designed for Large and larger creatures deal +1 base damage die per size larger.
For example, a longsword is normally 1d8 so a large longsword would be 2d8 and a huge longsword would be 3d8 and a gargantuan longsword would be 4d8 and so forth. A greatsword is normally 2d6 so a large greatsword would be 4d6, a huge greatsword would be 6d6, a gargantuan greatsword would be 8d6 and so forth.
Improved Natural Attack & Unarmed Monk Damage: Improved natural attack merely adds +1 base damage die as if you were one size larger. Monk damage adds only 1 die when increasing size even if the monk damage normally does more. For example, a monk that deals 2d6 with unarmed strike gets only +1d6 for becoming large.
Critical Hits and Vital Strike: Critical hits multiply weapon damage dice normally, but Vital Strike and similar effects do not. Vital Strike adds only the base weapon's base damage dice, not additional damage dice added for being larger. So a Vital Strike with a large greatsword would be 6d6 and an Improved Vital Strike with a large greatsword would be 8d6 and a Greater Vital Strike with a large greatsword would be 10d6. Vital strike with a large longsword would be 3d8, Improved Vital Strike with a large longsword would be 4d8, and Greater Vital Strike with a large longsword would be 5d8.