Morrowind:Vistha-Kai

Vistha-Kai is an Argonian knight and the Warden of the Corprusarium. He says that he once was a slave of Divayth Fyr. When his master freed him he stayed to help the wizard, first as a simple mercenary, but in time becoming a sincere friend and partner to his previous master.

On your first meeting him, he will let you into the Corprusarium but will warn you not to harm any of the inmates. Attacking one of them will cause him to turn hostile. While his dialogue says he enjoys hunting thieves, he never actually leaves his post, nor will he stop you from plundering the chests.

He wears a steel cuirass with matching pauldrons and gauntlets. He carries a steel war axe, a large kwama egg, and a sample of scrib jerky. Like all Argonians, he is immune to poison, has a resistance to disease, and can breathe underwater; otherwise he knows no spells.
 
Related Quests
Main Quest


Dialogue
Greetings:
"I am Vistha-Kai, Warden of the Corprusarium. I am here to warn you: do not harm the inmates. If you come to plunder the dungeon, you must endure their attacks, and take your chances with me, their Warden and Protector."
"You have been warned. Do not harm the inmates of the Corprusarium. If you plan to plunder the dungeon, you must endure their attacks, and mine."
''"You've killed one of us. And now it is your turn to die."  
"I am Vistha-Kai, Warden of the Corprusarium. And you have killed one of the inmates that I am sworn to protect. Prepare to receive your just punishment."  
-----
Background: "I am Vistha-Kai, Knight."
Corprusarium: "Lord Fyr shelters and maintains the victims of corprus disease here in the Corprusarium. He does them a great service, because no other could or would help them. He also does the world a great service by keeping them here where they can do no harm to others. The inmates are sad, distorted monsters, angry and cruel, and their sufferings are great, but they still live and feel, and I honor Lord Fyr's care and compassion for them."
endure their attacks: "Do not harm the inmates. I will not tolerate you adding to their suffering. Indeed, they are brutal and ferocious, and they will kill you if they can. But you are their guests, and you may not harm them, or you will answer to me."
plunder the dungeon: "For his own amusement, Divayth Fyr permits thieves to test their skills by attempting to steal the treasures he keeps below in the Corprusarium. The dangers are fearful. The inmates are savage, and they carry the most terrible disease on Tamriel. The treasures themselves are guarded by traps and terrors. And the guards, myself chief among them, will take great delight in trying to kill you. Those are the rules. Abide by   leave."
Warden: "I am the guardian and peacekeeper of the Corprusarium. I have spent long years in service to Lord Fyr, first as a slave, then as a free hireling, and now as a friend and partner. He has been kind and generous to me, and I take his interests, and the interests of those he shelters, to heart. The treasures of his dungeon are open to sport, according to Lord Fyr's whim, and you're welcome to try to steal them. But I, too, find great sport in hunting thieves."
Yagrum Bagarn: "Yagrum Bagarn is in the bowels of the Corprusarium. Pass through the gate and go straight across to the next door. He rides in a four-legged cart. He's not as dangerous as the other corprus victims. I doubt he'll give you any trouble."''

Notes
While Vistha-Kai isn't technically listed as Essential (you won't receive any warning for killing him), if you kill him before or while doing the Corprus Cure quest, his death will cause the quest to be unsolvable.