Oblivion:Mannimarco

Mannimarco, a High Elf necromancer, is the arch-nemesis of Vanus Galerion and the Mages Guild as well as being the leader and founder of the necromancer cult The Order of the Black Worm. With members of the guild leaving due to Arch-Mage Traven's stance on Necromancy, he has used this division to gain followers and launch an all-out attack against the Mages Guild in Cyrodiil. 

He can be found in Echo Cave, although only while the related quest is active. Once there, he will simply wait in his current position, in Echo Necromancer's Chamber, never even eating or sleeping.

He wears the unique but unenchanted King of Worms' robes. He is armed with a silver dagger and a unique artifact: the Staff of Worms. In addition to the latter, Mannimarco is associated with two other Elders Scrolls artifacts, both which appear in Oblivion: the Necromancer's Amulet and the Bloodworm Helm; the first was actually created by Mannimarco.  However, he lost possession of both artifacts to the Mages Guild. 

In addition to these weapons, Mannimarco also has powerful magic at his disposal.  He has a unique birthsign that provides him with permanent +100 Fortify Health, +20 Intelligence, 50% Resist Magic, Normal Weapons, and  Paralysis. He is able to cast the Expert-level spells Immobilize and Lightning Ball, the Master-level spell Summon Lich, and five random, leveled Necromancer spells.

As soon as you arrive in the Echo Necromancer's Chamber, he will immobilize you and start the following dialogue: ''"I see Bolor was unsuccessful in delaying you. Very well. I shall reanimate him once we are done here. Perhaps we shall chat for a while, since you really have no other options? I must say, I expected Arch-Mage Traven, rather than his star pupil. I am disappointed to see that he could not face me himself. I have met so many of his predecessors over the years. I developed a particular fondness for Galerion, ill-preserved though he may be. But here you are instead. Skilled enough to make it this far, which speaks volumes about you. Perhaps you'll be as useful to me as Traven would."'' If you say "I'll never help you!" He will say ''"Oh, my dear, I didn't mean to imply that you have a choice. I will make you another in a long tradition of Worm Thralls, and take my time in studying you. Your very soul will be forfeit to me."'' 

If you say that you'll serve him if only by having your life spared he'll say ''"I'm afraid you misunderstand.  I already have more servants than I need.  Your body will be preserved as a Worm Thrall.  Your soul is mine; I intend to study both to learn more about the source of your power." He will then conclude with: "Power, my dear friend. I seek power, and so I acquire and study those who have some degree of it. We are after the same things, your guild and I. Yet you worry about 'good' and 'evil' and do not accept they are manifestations of the same thing. So you brand me a villain, and make vain attempts to destroy me. I watch, and I wait, and I collect you when you come for me. Instead of drawing Traven out, I have received you instead. Perhaps I shall personally go and collect him when we are done here."'' He will then turn hostile and proceed to attack you. 
 

Related Quests


Notes
There is also a female test NPC named 'Mannimarco'. She is a Necromancer also armed with the Staff of Worms as well as Mannimarco's spells but is not found anywhere in the game.
Arielle Jurard of the Fighter's Stronghold official plug-in appears to have been a student of his.
It is possible to keep repeating the conversation with Mannimarco by activating him before he turns hostile.
Should you possess 100% (or greater) magic resistance and refrain from attacking him, Mannimarco will repeatedly attempt to paralyze you in order to initiate conversation. Once his magicka is depleted, he will draw his weapon and become hostile.
It's entirely possible to avoid the scripted dialog with Mannimarco and just kill him outright (which interestingly enough means Arch-Mage Traven's self-sacrifice was pointless) if you have a high enough acrobatics level and a ranged weapon with a blast radius of at least 10'. Start to approach him until he detects you and raises the bone wall. Immediately head back and jump over the bones and stand on the bridge area. He should continue to constantly walk into one of the bones as his script is being interfered with. If you have an arrow like "Arrow of Immolation" which has a blast radius and explodes on contact with certain surfaces, just keep firing it at the bones Mannimarco is walking into which will cause the arrow to explode on impact same as it does when striking an NPC. May take 8-15 arrows depending on bow used and Marksman level due to the bones buffering some damage, but the blasts will kill him eventually although there's no indication he's taking damage until he actually comments and starts summoning. Once he's dead, the bones retract like normal and the quest will update he's died.
It's possible to kill him by "rushing" him off the edge of the island, thus pushing him into the water.  He will swim back and eventually get back to you but lose some health to drowning.  Done enough times, he will die in the water.

See Also
Mannimarco, King of Worms: A book describing Mannimarco's history
: for general lore about Mannimarco