From Destinypedia, the Destiny wiki
Xivu Arath's Horde
The Oracle Engine
Summon Taken High Durability Rapid Movement Burn Projectiles Teleportation Hive Melee Drop Charge
An Ragaar, Son of Xivu Arath is a Taken Knight seen in the first part of The Oracle Engine mission. He, along with his sisters, were tasked with barring the way to the Oracle Engine from the Scorn, Awoken, and Guardians, which is where he'll meet his end by The Guardian. Assuming by name, he is a child of Xivu Arath.