From publisher blurb:
No Great Mind Has Ever Existed Without a Touch of Madness
With the Alienist, a new 20-level player character class for Labyrinth Lord (and other old-school fantasy role-playing games) you'll bring madness and mayhem to the gaming table. Part psychologist, part psychic - all insanity! By manifesting these powers of the broken mind the alienist is a dangerous ally or deadly foe for any adventuring party!
Alienist uses rules and options presented in the Advanced Edition Companion, which is available for free download.