Every creature has a finite amount of essence in their being, referred to as an essence pool. While essence is not typically expended when veils or other akashic effects are activated, a given creature can only devote a certain amount of their essence to any particular function. This is done by investing the essence into the chosen receptacle, which could be a veil, akashic feat, or other ability. Unless otherwise noted, investing or reallocating essence to or from a valid receptacle is a swift action.