History of Grask, the Consumed

Grask, the Consumed is a Taken Red Legion Phalanx and the original final boss of the Lake of Shadows strike. He was once a Red Legion Phalanx who was taken by an unknown Taker, presumably Savathûn, and he is the first Taken to hint that Savathûn controlled the Taken after Oryx's death.

Destinypedia states that he was replaced by Gor'ath Gath when the strike was revamped in Season of Defiance. Other sources do not confirm the replacement or its timing, and Destinypedia's Lake of Shadows page carries a Rework label, so check the current strike before relying on either version.