He spawns on the south end of Harpy Island, which is the one with a lot of broken collumn and arches, harpies, and bollos statues just south of Oceanus Haven.
He is almost always around--I've found that when I kill him, he's repopped before my health is even back to full yet.
He casts a mez and a DD from range, and he has a damage add shield. He doesn't hit particularly hard in melee, though.