Barrostrandt, the Ascended is a Reanimator boss creature. He is the target for the Order of Death's Vigil Bounty The Ascended, available after reaching Respected with Death's Vigil.
He can summon several (3-5) minions and is found in the Living Quarters inside the Warden's Hidden Laboratory.
Barrostrandt location
Barrostrandt, the Ascended