Transcendent Edde is a white phantom NPC available for summoning. He is only available in the Crown of the Sunken King DLC.
He is a generally helpful summon for the boss fight, as he has an impressively large health pool allowing him to tank, and can deal respectable damage with his Black Dragon Greatsword. He will also drink Estus when injured enough.
Upon being summoned, he will perform the "Bow" gesture to the player. He will also do it once Sinh has been defeated, provided he survived the battle.