"There are many stories about that blade, my son. Almost none of them are true. That's probably a good thing; the world is a better place for not knowing the origins of Kalthalax. Yes, our ignorance is a blessing... the birth-flames of that sword must have been emerald green with wickedness."
Kalthalax... slayer of Demons, Devils, any and all of infernal heritage*. However, the origins of this blade were not slaying Demons but transferring their infernal essence to a new host... a chosen one. Kalthalax is the sword's human moniker, named after the crusader from another world who drove his men into Hell's circles, savagely routing the soldiers of darkness in their very home. But Kalthalax has another name, a secret name given to it by Sydaac the Elf who forged it from an ultra-telluric metal that none had ever seen before or since. It had strange properties; chiefly, the power to house a Demon's soul.
Forged into a formidable rune-blade, the unholy vessel was able to draw and keep the infernal essence or tenebrae until needed. The Elven swordmaker and worshiper of Voorthal'nyggura named it after the first Demon to break through their fiery prison; his name Kort'thalis! Kort'thalis and his brothers conquered a third of Razira before Yogsoggoth and Tsathag'kha dreamed themselves back into reality.
Kort'thalis abides, its black aura a tell-tale sign of the thousands stored within. Voorthal'nyggura's servants prepared a patchwork golem of flesh to house the collected essence. A thousand years ago, this stitched, grafted, and misshapen giant was to be the god's champion. Soon after it was fashioned, the creators changed their minds. The blade's custodians began to serve the sword more than their own god, each hoping to evolve into the prophesied chosen one. They decided to keep Kort'thalis for themselves, knowing its power over Demonkind. Might making right, they settled age-old vendettas and used the rune-blade to reign in Hell... for a time.
The sword was lost towards the end of their Demon wars, after a string of long and bloody battles. An Elf, descended from Sydaac, claimed it. This Elf recognized the ancient glyphs upon its lethal visage. He carried it back to the mortal world, bequeathing it to a youthful, dark eyed stranger, so humanity would have a chance for survival.
Once the wielder is aware of the sword's true name, he may claim its hidden powers.
* Upon rolling a natural 20, the sword decapitates its infernal target, stealing that Demon's soul in the process.
* Those Demons struck down by Kort'thalis are absorbed by it. All their tenebrae is swallowed, except for a fraction of it; the smallest part flows through the swordsman as he delivers the killing blow. When Kort'thalis destroys (or converts) an infernal being, add up their Hit Dice. For every 23 Hit Dice collected, the swordmaster receives an additional point towards one of his ability scores. Example: Veen the fighter has slain 21 HD worth of Devils and Demons since attaining Kort'thalis. The fighter destroys yet another Demon, this one 6 HD. Veen only needed 2 more points before reaching 23. He chooses to raise his strength from 16 to 17 and starts the tally over again at 4 HD, because of the remainder.
* Upon rolling a natural 1, the Demon slayer expels a portion of its built-up essence. Kort'thalis surges with a lurid, violet-red glow as reality becomes overshadowed by darkness. Everything within a 30' radius is corrupted by evil, especially the wielder. Lawful (or good) individuals take 6d6 damage.
But there's another downside - tenebrae is radioactive and, given enough exposure, even cancerous. When a wielder has struck down 100 HD worth of Demonkind, he becomes Chaotic (if he hasn't yet traveled down that road voluntarily) and transforms into a hideous mutant from beyond this universe. See the following table for specific (and more accessible) results...
1. Flesh as black as moonless midnight; completely hairless; winged.
2. Aqua skin tone, worm shaped, with white hair and eyes... no mouth.
3. Some cross between a fly, wasp/hornet, and spider.
4. A semi-corporeal violet gas.
5. A Demon with crimson scales, horns, hooves, barbed tail, forked tongue, and wild yellow eyes.
6. Ivory skin and hair with tentacles sprouting in odd places, blood red eyes, and extremely long fingers.
Original sword artwork by Timothy Shodukari with digital enhancement by Dave Bergamoth.