Vissar is a NPC in Divinity: Original Sin 2.
Not sure why, but on one return pass through the fort before leaving the area I found Vissar just dead on the ground. I'd been extremely careful to not harass any townsfolk but he was dead on the ground. My best guess as to why this happened is he might have tried to help me in a large fight but not actually been in range of the fight itself and died to someone that was hostile to me. Unfortunate.