Knowledge of the physiology of creatures in general. This is an umbrella skill that encompasses a vast suite of sub-skills for particular types of creatures. This parent skill represents generalized knowledge that applies to all creatures in the world.

Examining corpses a corpse (with an Autopsy Kit in the inventory) will raise the relevant creatureanatomy sub-specific anatomy skillpertinent to the slain creature.  As these sub-skills improve more details will be revealed about the creature, such as their Abilities and their particular weaknesses (eg. Weak to Poison, Resistant to Slash damage).