Furlinastis

Furnalistis is a shadow dragon who lives in a swamp on the Plane of Shadow. His body is covered in moving shadows which twist into the faces of the souls that are trapped within it. These souls keep a shard of Masks divinity which was stolen by Kesson Rel trapped within the shadow dragon's body. Erevis Cale first meets Furnalistis in the swamps of the plane of shadow after he instinctively teleports himself, Drasek Riven, Jak Fleet, and Magadon out of the fane of shadows before it collapses.

Ties with Mask
When Furnalistis meets Erevis Cale for the first time after a heated battle. he recognizes Cale's sword Waveshear as the weapon for the "First" of the age. He then says "The promise has been fulfilled" Which he refuses to elaborate on and then he flies away.