Of all the auspices, the Ithaeur undergoes the most drastic change between human life and his new existence as Uratha. Before, even if he believed in spirits, he didn’t see them on a regular basis. Now they are everywhere. Everything has a spirit, and every spirit is hungry.
Being a crescent-moon means literally never being alone. The Ithaeur is always being watched by a thousand ephemeral eyes. He has to become comfortable with that, because nowhere in Flesh or Shadow is without spirits. The crescent-moon therefore embraces his many companions, includes and acknowledges them, and does his best to live in accordance with their laws. To do otherwise is disrespectful, and disrespecting spirits can be fatal.
The Ithaeur is a shaman. He is set apart from every society to which he belongs. He is no longer human, of course, but although he has awakened to his nature as a creature of spirit, he is not a spirit — and the denizens of the Hisil are happy to remind him. But the trauma of the First Change often pushes the Ithaeur so far away from his humanity that he identifies more as spirit than flesh and, in many cases, forgets that the best course of action is to take the middle ground and be Uratha. He behaves strangely even for a werewolf, observing bans that do not actually affect him, and in the process becomes closer to the spirits than is healthy. This makes him a valued part of the pack and the tribe, but also makes him an outsider. The Spirit Master is the werewolf other Uratha seek out when they have need of his skills, but he is not the first choice for socializing. Regarding those Ithaeur who act more like spirit than flesh, other werewolves sometimes say “duth thu Uremehir” (“he was born to speak the First Tongue”).
Regardless of what his pack might say about him, though, the Ithaeur plays a crucial role in the Sacred Hunt. When hunting spirits the advantage is obvious, but even when hunting more corporeal prey the Ithaeur can use his unseen allies to best effect. A skilled crescent-moon can see through a spirit’s eyes, wake the slumbering spirit of an object to make it betray its last user, and borrow the power a spirit has over its own areas of influence. He can track prey using the disruptions or activity in the Shadow as a guide, and, if he wishes to truly hurt his prey, he can call up spirits keen to possess or Claim.
The Ithaeur is called a Spirit Master among Uratha, but only a truly arrogant werewolf would claim the title. Weak spirits are easy enough to control and destroy, but the rulers of the spirit courts are like unto gods, far above the ability of any werewolf to command. Lest the werewolf forget, the weak and pathetic spirits he bullies today might report him to their more powerful counterparts tomorrow. An Ithaeur who does not check his wards and spiritual proscriptions is likely to be yanked into the Shadow and torn asunder. Long-lived and powerful crescent-moons, then, are truly masters of the spirit.