"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.
After encountering The Venship on Kiston, Promissa struck a deal with the group. Because she was a necromancer, and because the group had already suffered casualties, Promissa promised to help lead and guide the team on a mission that would lead them off the island, but needed to resurrect two of the dead, Alexias and Edgar, in order to properly protect the group and to have more helping hands on the team. While this lead to the gruesome resurrections of a skeleton Alexi and a zombie-like Edgar, the team ultimately decided it was for the best, and the 4 living + 2 dead were able to work together and get to Promissa's abandoned campsite further inland.
