Anima is the mystical life force of Anhet. Most in-game actions, including using the Gauntlet, the Sphinxes, and using many powers have a certain anima cost, displayed in parentheses next to action link. Once a player runs out of anima, he can do nothing but post in the Underworld section of the Commune boards.
Anima is regained in several ways. The first, and most simple, is to wait for the replenishing of anima and vitality that occurs every night. The second way is to rest, although this logs you out of the game for four ours and does not grant very much anima. You can also get anima from others players who use Sacrifice on you, from using the Gauntlet, from Ifrit, and from the Sphinxes is you have the Hathor skill Blessing