Ashangu, The Summoner, is a Unique Fallen Shaman found in the Dahlgur Oasis in Act II of Diablo III. He is always spawned on a small cliff above the pond. Approaching the pond will cause Fallen Lunatics to jump out of it.
In combat, Ashangu has Knockback and Frozen affixes, and in addition summons Fallen Lunatics at his side.