Every campaign needs an evil mind controller. And what could be more unequivocally evil than genocide?
[AD&D-Specific] Bzaran the Genocide, human male, Str 18 Dex 18 Con 19 Int 19 Wis 19 Cha 19 Align LE Hp 104. Enchanter, level 18; Psionicist, level 21.
Bzaran used to be Warden of the Institute of Enchantment in Atlantis. Then, to everyone's amazement, he suddenly resigned from his post, appointing his pupil Genesse Stapo as his successor. (Another of his former pupils, Laiyriani Duerlmityr, is currently head of the Learned Society of Conjuration, Binding and Enchantment.)
Bzaran's change of career was directed by the Gods of Atlantis. Previously, Bzaran had not been particularly religious - like many other control freaks, he paid his respects to Frark the Controller, a lawful neutral deity with a major temple in Atlantis. All this changed when he received a vision from several Gods of Atlantis informing him that (a) he should henceforth devote himself to destroying every mind flayer in the Fifty Worlds, and (b) as and when the last mind flayer is destroyed, he will receive divine ascension.
Immediately following this vision, Bzaran resigned his post as Warden of the Institute of Enchantment, appointing someone trustworthy as his successor. He then set himself the initial task of studying psionics, in order that he would be better-prepared for his duty.
Having completed his study of psionics, he then set out to destroy every mind-flayer in the Fifty Worlds.
He is doing rather well. There are no longer any mind flayers on Delta, the world on which the City of Atlantis is to be found. So, although Bzaran may turn up anywhere, he is less likely to be found on that world than elsewhere.
Bzaran is more lawful than evil. He respects the laws of Atlantis, and the reasoning behind them. He will not use violence against anyone whom the laws of Atlantis would protect (this includes anyone who appears roughly humanoid, but obviously excludes mind flayers). If attacked, he will use his spells and mental powers to defend himself.
Bzaran remains a control freak. Given the opportunity, he will enslave almost anyone he meets (probably using psionic domination followed by psychic surgery, although he has several other options), and compel them to kill any mind flayers they meet. He will use other methods on psionicists or people with psionic wild talents. As a professional courtesy he will not enslave others, whether wizards or bards, who specialise in enchantment, conjuration or illusion, unless they obstruct him in his quest. Since he is on a sacred mission decreed by several Gods, he expects lawful priests to obey him anyway, without being forced to.
Bzaran is not a nice control freak. He likes to humiliate his slaves, to emphasise how helpless they are to resist his control. However, he never causes them physical damage.
Bzaran no longer carries or uses magical items. When he left the Institute of Enchantment, he handed everything he owned, including his spell-books, over to Genesse Stapo.
Bzaran carries all the spells he is ever likely to use in his head. He can prepare any spell he wants from memory. As a specialist enchanter, he never uses spells from the schools of necromancy (he thinks, like many Atlanteans, that necromancy is disgusting) or invocation/evocation (he despises those who put their trust in violence).
One of Bzaran's psionic powers enables him to cast wish without any adverse side-effects. On any day when he has an hour and a half to spare, he will cast wish to benefit himself in some way, and then re-prepare it. He has already boosted his attributes and hit points as far as he dares, and is now working on more subtle ways of self-improvement.
As a gift for his fanatical devotion to his sacred duty, the Gods have granted Bzaran the power to cast rigid thinking (3rd level priest spell) at will (once per round, on only one creature at a time, saving throw negates).
As an additional granted power, whenever Bzaran addresses someone by name, he can command (1st level priest spell) that person (once per round, on only one creature at a time, saving throw special). The name need not be the target's true name, but it must be one that the target is currently using. He will often follow the command with rigid thinking (although, even if affected by the command, the victim is entitled to a second saving throw to try to resist the rigid thinking).
If Bzaran is uncertain about anything, it is what the rules of his cult should be after he receives divine ascension. He has heard Pamina preach, and he understands and approves of the arguments in favour of vegetarianism without being entirely convinced that everyone should practise it.
Bzaran's real functions in the campaign is to scare player characters shitless.
If the player characters get truly out of hand, have Bzaran show up to show them what it feels like to be really, really scared.
Bzaran is also a reminder of which species is the most monstrous of all. He is, of course, also quite good at disposing of mind flayers.