Just did some brainstorming on other ways you could use immortality. These come from a mix of inspirational games/movies, and my own dark thoughts. [EVIL] should be so, and such I try to think of all the things that we consider Socially and Morally abhorrent. Of course, these ideas are made "safe for womens" before posting here. Those that wish to can follow the ideas to their obvious dark conclusions by themselves.
I'm working on the 40k Necromunda mod so wont have time to actually mod any of these ideas. Feel free to use them for your own mods.
Immortalized in Stone. The necromancer becomes made of a very strong stone. He seeks out creatures, alive and dead to remake into stone warriors. Themes include Aztec magic, raw earth elemental, technomagical mechanisms of stone, power crystals.
Energy transmogrification. The necromancer becomes as pure energy but still craves contact with the phyisical realm. He possesses creatures and corpses directly, turning them into husks and filling them with his essence.
Blood tide. The necromancer unleashes a pox upon the world. His invasions include vermin which spread a long lasting and contagious virus that weakens all creatures it infects. Protecting your fort from infection through quarantine is a possibility since the pox moves so slowly. Other attackers have the ability to control infected dwarves, or detonate them spontaneously in a cloud of miasma.
Clad in technology. The necromancer becomes obsessed with modifying the body for advanced purposes. Aethetics for all purposes are created and grafted onto cultists to create abominations of technology and flesh. Some of these are for mundane tasks, others for war. The Necromancer himself becomes clad in a thick armor plate with built in weapons.
Melding of the Flesh. This secret sees the necromancer shaping the very flesh itself as putty. Constructs are made from living specimen, not corpses, perhaps even with great beauty. That said his armies are powerful but non-contageous. The necromancer can modify his own appearance at will, becoming huge or tiny.
Control the feeble mind. This type of necromancer rules through controlling the thoughts of living creatures. His slave armies do his bidding without concern for their own safety. He enjoys a large harem in his tower, free labour in his workshops and a large standing army. Lower class, weak or injured slaves are made into food for the more useful castes. Those who stand before him are either slain and eaten, or survive to be enslaved themselves.
The Surgeon. Frankensteins creator. The Graverobber. This variety of necromancer digs up or steals parts to create huge abominations through surgical and technomagical means. He is a frail, clever necromancer who never fights directly.
The death mother/geneticist. A necromancer who fills his tower with great pulsating wombs which frequently birth litters of loyal creatures. The weak are killed while the strong are force-bred with each other to produce enhanced seed for the wombs. The necromancer is the master of evolution, building greater and greater creatures with every generation. Waiting is not an option against this evil.
Celestial dreams of perfection. Immortality through ritual and prayer. This necromancer dreams of a utopian world of immortality where nobody is hungry or want for anything. His means however are far darker. Somebody has to do the dirty work in his utopian society and it certainly wont be him or his closest cultists. His warriors are straight, glorious and deadly. His empire is enlightened and intellecualism is promoted, giving all in it access to high technology methods. All that is except the lower castes...
The Tyrants gift. Ruling through brute force, the tyrant is himself immortal and has the ability to resurrect his minions once they die. This bestowed immortality is only fleeting tho, and once you have succumbed you must remain loyal else your body start to decay. The will to survive in humans is a strong one, and many have chosen a life of blackmail over death. His workforce is whipped until they are on the edge of death, then offered this Dark Choice.
Entombed in the earth. This necromancer extends his life through entering statis or torpor underground, only rising to give a command or lead an important battle. His enhanced minions can dig swiftly and have enhanced night vision. When outnumbered they will retreat into the earth (retract into shell) and wait for reinforcements to arrive.
Back to rule, againThe necromancer himself is possessed by the spirit of an ancient necromancer. He brings forth spirits of great skill to re-inhabit the bodies of his cultists, improving their prowess many times over. Weaker spirits may be tempted to inhabit trolls, ogres or even the lowly badger, as they are all desperate to feel the touch of the material plane once again.