From Destinypedia, the Destiny wiki
The Abyssal Champion is a Ultra Hive enemy that appears during the Heroic version of the Witches' Ritual Public Event on Titan along in a challenge in the Dreaming City. The Abyssal Champion can only be summoned after destroying the shielded crystals on either side of the portal during the ritual.
The Abyssal Champion functions similarly to Alak-Hul, the Darkblade, as the Champion will at first slowly march toward the nearest Guardian and take massive swings with its large axe. In addition, the Champion will periodically vanish for a brief moment only to teleport and reappear to launch a surprise attack. Once dealt enough damage, the helm of the champion will vanish, revealing a deformed face and will become enraged and charge his foes.
List of appearances