Folduin was a strict Lord of Briskwater, who oversaw its defenses and took whatever measures he had to keep it safe. He died under mysterious circumstances, and not all family members were invited to his burial.
As revealed by his son, Corym Caerlinn, Folduin staged his own death in order to pursue other goals. An illusion was left in place of his corpse in the family mausoleum to fool anyone investigating, while Folduin pursued his dread purpose, now working for the Circle of the Drowned.
By scrying on him, Mirasol Rosneth found out that Folduin had taken the shape of Phebus Glimmergold to lead an expedition into the wilderness, funded by Ezrael Limberhausen. Serani and Myllo Shapewater were also on this expedition, and only learned later that something was amiss with the way that their expedition leader behaved.
Farhold Keep
Valkyrie found Folduin and Celydia Caerlinn as she escaped from the demiplane of Enma and Yokai. Folduin taunted her, and eventually attacked her with a hovering black blade, before Celydia knocked her unconscious.