Even ghosts tell ghost stories.
The process of becoming a lich is fraught with difficulties, many of them intelligent. One story that makes the rounds may only be a cautionary tale meant to deter would-be undead, but its persistence suggests otherwise.
The story goes Toh Var-Im is himself a necromancer, of great skill and a cruel idea of justice. When he hears that an aging wizard is seeking lichdom, Toh Var-Im presents himself, appearing as another lich, offering the final keys to the elixir and prepared to strike a bargain of mutual assistance throughout the long centuries to come.
The formula is verifiably functional, yielding a prepared body that will be able to retain a soul, and arcane protections that will keep a dying soul from exiting its plane, instead allowing itself to anchor to such a vessel. The process of completing the elixir involves a multitude of sins better left unspoken.
The price he charges is threefold: first, a goodly quantity of high-quality enchanted items; second, a mutual pact never to aggress against each other; and third, blood from the still-living wizard, for the making of a token to be called in for a single, finite task at some indefinite time in the future.
Those who accept find that the third term is the one with the trap. When they perform the rite, they find that Toh has already prepared a suitable prison for their soul, using the blood that they gave him. When they die they are inexorably drawn into his clutches.
Over the years Toh Var-Im's library of captured souls has grown in number; for a near-lich is a powerful wizard, but by no means necessarily worldly-wise, and not everyone is both lucky and depraved enough, or has enough time and resources, to work out the formula entirely on their own, or locate it in the coded manuals of the darkest studies. Those who seek undeath to escape the grasp of Hell might not even find Toh Var-Im's captivity terribly burdensome: he consults his captives for their knowledge of various lores and histories, and even provides them with new books on occasion, along with orders to meditate upon this or that thorny question of thaumatology. They lack any capacity to experiment, of course, but their theoretical insights can prove most useful.
In addition to his growing library of minds, Toh Var-Im gains another very useful acquisition: knowledge of a recently failed attempt at lichdom. A few words to one or two sufficiently skilled parties of adventurers is usually enough to convince one of them to essay the well-guarded sanctum of the dead wizard, defeating his guardians, disenchanting his traps, and mapping his labyrinths. He quite amicably pays the adventurers for their work, taking a fair share of the old wizard's usually extensive magical treasure. More importantly to him, he also takes possession of one more very carefully preserved dead body complete with the animating undeath enchantments, suitable for immediate occupancy by a spirit capable of any sort of possession.
After all, Magus Var-Im only appears as a lich.
Nice work, especially the library of minds. There aren't many great lich-like NPC's, except Skall and the alhoon in Sigil that Rip wrote.