Furlinastis

Furlinastis was a shadow dragon who lived in a swamp on the Plane of Shadow. His body was covered in moving shadows which twisted into the faces of the souls that were 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 Furlinastis 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.