"Out of all the Re-Animators I know, you have always been the strongest" - Fermi's last words to his ward
Promissa was a necromancer serving under the lost god Vecna in the early BR era. She called herself a "Chaser of Secrets".
About
Promissa was stranded on the island of Kiston...purposefully. She and her faction of Vecna followers were on a mission to divine the secrets of the realm for their God of Secrets. Knowing the center of the realm was an unmapped death trap, their team, led by the necromancer Fermi, drove their ships directly into the maelstrom, banishing themselves into the locked continent.
Promissa considered herself a "Newling" of the clan, and expendable, which is why she volunteered on the mission to head into Kiston in the first place. She begged to be given up to the Draco-Orc sacrificial ritual in place of her mentor Fermi, but the others, a group known as The Venship, voted that Promissa should stay alive, as she was full of "promise", and Fermi would be sacrificed.
Promissa, or an associate of hers, gave the name "Vern" to creatures later known as Wyverns.