SRD 21

SRD 21, also known as the System Reference Document 21, is a term that does not have a specific meaning or context in a general sense. Without further information, it is difficult to provide a specific description.

However, “SRD” often refers to a System Reference Document, which is a set of rules and guidelines provided by a game or system developer for use by players and game masters. These documents typically outline the core mechanics, character creation rules, spells, and other essential elements of a role-playing game or system.

If you are referring to a specific SRD 21 related to a particular game or system, please provide more details so that I can offer a more accurate description or explanation.