Furlinastis

Furnilastis 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 once kept a shard of Mask's divinity which was stolen by Kesson Rel and then trapped within the shadow dragon's body.

Ties with Mask
When Furnilastis met Erevis Cale for the first time, he recognized Cale's sword, Weaveshear, as the weapon belonging to the "First" of Mask. He then healed Cale and his companions of their wounds and said, "The promise has been fulfilled", which he refused to elaborate on.