Nightmare of Skolas, Kell of Kells
From Destinypedia, the Destiny wiki
The Nightmare of Skolas, Kell of Kells is the Nightmare version of Skolas, Kell of Kells, who tried to bring all of the Fallen Houses under his control, but failed. Now arisen as a Nightmare, representing the Essence of Pride, Guardians are forced to face against the Wolf Kell once more.
Skolas is the second Nightmare you hunt in Shadowkeep and is located in deep within Taniks' destroyed ketch in the same room you fight Taniks, the Scarred and Driviks, the Chosen. Like most of his Nightmare counterparts, Skolas fights very similar to how he did in the Prison of Elders but with the new Nightmare ability to turn invulnerable and summon Nightmare Fallen.