Deathfin Zokuno is a Deluvian Deathfin from the Blood Mountain monastery, who has mastered the Scroll of Haya-sa's Impatience. This has given him the ability to cast Haste as a swift action and then somehow absorb the spell into his blood, preventing it from being dispelled. In short, he's Professor Zoom.
His most notable mission (from a TDDC perspective) was to kill Angel's Master, who had been killing Deluvian commanders on behalf of The Organisation. He completed this task with ease, seeming more to toy with his prey than actually fight. Witnessing this from a hiding place nearby traumatised young Angel, making her hatred of the Deluvian Empire more personal than professional.
A copy of Zokuno later appeared in the Realm of the Albtraum as one of two final bosses The Party could choose between (the other being a copy of Deathfin Vazilai). Despite demonstrating a number of BS powers, including the ability to duplicate himself, the duplicate was slain and The Party escaped, killing the Vazilai clone on the way out for good measure.