Morrowind:Dagoth Gares

Dagoth Gares is a minister of the Sixth House who can be found at the shrine of Ilunibi, provided you are on the related quest.  When you first meet him, he will greet you with a message from Dagoth Ur, and then attack.  When you kill him, you will be automatically infected with Corprus. This is part of the Main Quest and is completely unavoidable.
 
Related Quests
Main Quest


Dialogue
Dagoth Gares has some unique dialogue, which he will greet you with when you approach him.
Greetings: 
''"The Sixth House greets you, Lord Nerevar. Or %PCName, as you call yourself. I am known as Dagoth Gares, priest of Ilunibi Shrine, and minister to Sixth House servants. My Lord, Dagoth Ur, has informed me of your coming. I wish that this time you had come to honor your Lord's friendship, not to betray it."
"Yes, Lord Nerevar? What would you ask of me? Would you hear of my Lord, Dagoth Ur? Or of the Sixth House, or of Sixth House servants?"
Dagoth Ur: "Dagoth Ur is the Awakened Lord of the Sixth House, come to cast down false gods, drive foreigners from the land, and restore the ancient glory of Morrowind. He bids you come to Red Mountain. For the friendship and honor that once you shared, he would grant you counsel and power, if only you would pledge that friendship anew. The path to Red Mountain is long, and filled with danger, but if you are worthy, you will find there wisdom, a firm friend, and all the power you need to set the world aright."
Ilunibi shrine: "Ilunibi shrine is just a small, quiet retreat for Sixth House servants, a place to contemplate and grow strong and wise in Lord Dagoth's ways. Here we share the sacraments of flesh and blood, and dream the dreams of our Lord. This and other lesser shrines are hidden from prying eyes throughout the land. But the greatest shrines of Sixth House servants lie beneath Red Mountain, in the citadels of our Lord and his close kin."
Lord's friendship: "Lord Dagoth gives me these words to say to you, so you may give them thought. 'Once we were friends and brothers, Lord Nerevar, in peace and in war. Yet beneath Red Mountain, you struck me down as I guarded the treasure you bound me by oath to defend. But, remembering our old friendship, I would forgive you, and raise you high in my service.'   My Lord Dagoth bids you come to Red Mountain. For the friendship and honor that once you shared, he would grant you counsel and power, if only you would pledge that friendship anew. I am not your Lord Dagoth, yet I, too, would say to you... Do you come with weapons to strike me down? Or would you put away your weapon, and join me in friendship?"
our enemy "Lord Dagoth would far rather have you as a friend than as an enemy. But until you submit to him, Sixth House servants will treat you as an enemy, and try to destroy you. If you wish to be our friend, first you must go to Lord Dagoth in his citadel on Red Mountain, and make your submission."
Sixth House: "The Sixth House was not dead, but only sleeping. Now it wakes from its long dream, and with its Lord, Dagoth Ur, it comes forth to free Morrowind of foreign rulers and divine pretenders. When the land is swept clean of false friends and greedy thieves, the children of Veloth will build anew a garden of plenty in this blighted wasteland."
Sixth House servants: "Forgive the rude welcome, but until you have declared for us, we must treat you as our enemy. The Sleepers and Dreamers are newly come to Lord Dagoth, and not yet blessed with his power. But the Children of His Flesh, they are deep in the heart of his mysteries. Their bodies swell to contain his glory, and to yield the rich sacraments of our Lord's feasts. And we are the least of his servants, for Ash Poets, Ascended Sleepers, and Ash Vampires stand high above us in the Lord's bountiful grace."

Notes
If you talk to any of the Ash Ghouls at Kogoruhn, they will tell you that "The soul of Dagoth Gares is among us. You have broken his body, but his spirit is with us in our waking dreams" even if you trapped his soul earlier, or if you have not killed him yet.
Killing Gares will bring up an on-screen message: "With his dying breath, Dagoth Gares smiles and curses you. 'Even as my Master wills, you shall come to him, in his flesh, and of his flesh.'"''