Avatar Spirits

In game terms, avatars are powerful free spirits that can act as a magician’s spirit guide. Attacking or using magical skills against an avatar is usually futile, as it can result in the magician being transported to the metaplanes, unable to use magic for a time, or some other consequence of the gamemaster’s choosing. If in danger, an avatar spirit will instantly vanish to the metaplanes.
Avatar spirits are intended to be used for roleplaying opportunities. They can act as a warning of impending doom or they can play devil’s advocate. In any case, an avatar spirit should never be something players can exploit.

(SG, 202)