"When I first beheld the corpse raiser, I thought myself capable of defeating him. Then he reached out his arm, and the ground in front of him was bathed in a spectral light. The bones of men and beasts rose from the earth and advanced on me."— Lorath Nahr(src)
Corpse Raisers are Reapers, and can be distinguished easily by their color (dark green). They hover above the ground, but do not possess extra speed or the ability to fly over terrain.
Their own ranged attack is very slow and deals Cold damage, but it is unavoidable and always hits. Instead Corpse Raisers prefer creating glowing fields of green light over the ground in front of them every few seconds. From these fields, a few undead minions emerge (Risen Bones and Canine Bones), which are slow, fragile and weak. The total amount of minions a single Corpse Raiser may summon is limited. The green wave also deals small Cold damage.
Upon death, Corpse Raiser spawns 3-4 Vile Bats, identical to normal ones, but spectral green in color. Some Elite Corpse Raisers do not have this ability.