Haestus d'Cannith was the overseer of a House Cannith creation forge deep within a mountain near the border of Cyre and Breland. Haestus also had an interest in necromancy, and was investigating ways to combine the necromantic arts with House Cannith's artificer skills. They worked without direct oversight with House Cannith officials on new types of warforged prototypes.
Before the end of the Last War, a group of Karrnathi irregulars discovered the location of the facility. Realizing its importance to the Cyre war effort, the Karrnathis collapsed the facility, trapping all of the artificers within beneath tons of rubble. Haestus and his artificers died a slow death.
The exact location of Haestus' forge was lost in the fall of Cyre during the Day of Mourning; the same day that killed the Karrnathi irregulars. Haestus rose from the death as a forgewraith, and continued the mission he had in life: creating warforged prototypes.