This Dargean was mere shattered armour after a previous visitor had defeated them in battle. But upon the return of its shield, and a Dargean weapon, the being reformed when one of the door's seals was activated. The residual magic of the ancient creature reawakened to defend it's sworn purpose.
While the party were initially attacked by this individual, they were surprised when they could communicate with it in the common tongue. Knowledge was exchanged in place of blows, and an ally was gained for a time. That was until the corruption took hold. A magical affliction that is not understood by the Dargean can turn them into one of The Tarnished, a sect of Dargean turned to evil deeds, twisted by some force beyond.