Size

Size is a mechanic that will affect many actions against things.

Overview
There are 7 size categories that are used to determine something's size relative to something else, which is called the origin. Sizes are measured by total size, not necessarily height. Unless otherwise stated, the origin is assumed to be an average human. The examples below are given with this in mind. As these sizes are relative, if you were to take the origin as a dog for example, a human would be considered large, and a mouse small.
 * Diminutive or D - Something that is likely barely noticeable to the origin. Anything smaller than an ant. This is a catch all category for things that will almost certainly be unable to exert any consequential force onto something of the origin's size without monumental effort.
 * Tiny or T - Something that is far smaller than the origin. Roughly the size of a bug or a mouse.
 * Small or S - Something that is smaller than the origin. Roughly the size of a dog or a cat.
 * Medium or M - Something that is roughly the origin's size.
 * Large or L - Something that is larger than the origin. Roughly the size of a very small house or a tree.
 * Giant or G - Something that is far larger than the origin. Roughly the size of a building or a small hill.
 * Colossal or C - Something that is simply beyond the origin. Anything larger than a mountain. This is the mirror category to diminutive, where it's anything that the origin is very unlikely to be able to influence in any meaningful way.

Scaling
The main use of size is in scaling actions towards other categories of size. For example, if a human was to deal damage with a straight sword to a pilgrim or something else that's considered large to them, the damage would be dealt as a small weapon- as, to the pilgrim, a regular straight sword is considered to be a small weapon. Similarly, if the pilgrim was to use a regular straight sword, it would be classed as a makeshift small weapon and would deal less damage than either a straight sword or a dagger that was designed for them. However if that pilgrim was to attack a human, they would still take damage from a makeshift medium weapon.

This scaling is taken into account with any action, not just damage related actions. If a medium creature attempted to grapple a large creature, it would take great penalties on trying to doing so, and would instantly fail on anything giant or larger. Additionally, larger things are far easier to detect, so any focus or detection checks against large or larger creatures will be far easier, with colossal creatures being totally exposed, and even counting as large events more often than not purely by existing.

Equipment and Consumables
Size will also affect attempting to use any equipment or consumables that are not scaled to a creature's size. For the most part, equipment will simply be unusable by size categories outside of its intended use, as a creature whose hand is the size of a house will be unlikely to wear a ring that was designed for a human.

Additionally, any consumables may be affected by size, but this is not certain. While food need will largely scale with size, certain creatures will require far more food based on their activities. A creature that is constantly shifting might require more food than a large creature that simply knits. Additionally, different tiers can exist on a whole different time scale, or might not even require food. As for potions and the like, it will largely depend on how the concoction functions as to if it will effectively scale with size or have a constant effect regardless.