Though it is speculated by some that the immortals of Theliad might be descended from true Inadasir blood, and others have suggested that they might be avatars of some sort, the reality is a bit stranger. Deep in the bowels of an ancient cavern in the Agardash Mountains there lies a special vein of arcane crystals called the Black Kyanite. This particular source is almost utterly black unless under strong light, revealing a deep, dark blue quality to the stone. The Black Kyanite appears to have strange properties, not unlike the divine Zodiac Stones, in that those who even touch the stone are gifted with great boons as well as immortality. The ability of one to make something of such a gift is highly dependent on the recipient of the gift, and many fail to even survive the initial touch of the stone. Others are wracked with curses and disease worse than the gifts bestowed; the ones who are able to harness the power of the Black Kyanite are most likely those few immortals now known to be like demiurges to the Theliadics.
Black Kyanite can be found in only a few locations. Some is known to have been stolen away and is kept in an ancient dungeon deep beneath the city of Zheranos by the Canerous King Azeros, who himself has been bestowed with immortality at a terrible price. The lost Cavern of of the Agardash Mountains is the source of the purest and most powerful Black Kyanite, and it is believed that each of the “true” immortals of the land visit this cavern, and possibly took a piece of the powerful stone with them. Other sources of the stone may exist, and one rumor is that the ground beneath the ruin of Afar is riddled with impure versions of the stone.
If someone comes in to contact with the substance it will grant them a Boon, and also a Curse unless they succeed at a DC 21 Wisdom save, or sometimes a DC 21 Constitution save if the desire of the intended recipient of the boon seeks a great physical enhancement. Failure still grants a boon and immortality (no longer ages), but also a curse. Success, which happens rarely, leads to the boon and agelessness without a major curse, though debilitating side effects of the boon may still be evident.
The stone can be touched once a year to gain further boons (and curses), though each subsequent effort to do increases new saves by 1. If the save is ever critically failed (natural 1) the subject is killed immediately and transforms into Black Kyanite with all the properties of the stone. On a natural 20 the subject always gains the boon with no curse.
Characters who undergo this transformation gain the following perks from touching Black Kyanite:
1 Boon (see DMG for samples, or see more below)
Gain immortality (ageless; still can die of unnatural causes)
Gain one minor impairment as a side effect of boon (example: ability to cast burning hands at will also requires PC to sleep on nonflammable material at night or they catch on fire)
On Save Failure Gain Major Curse (see chart below)
Sample Curses from the stone include:
1 Lose immunity to disease and roll at disadvantage on disease saves
2 Lose eyesight
3 Lose hearing
4 Become hideously deformed (disadvantage on Charisma and Dexterity Saves)
5 Grow 1D3 extra eyes
6 Must concentrate or turn into a blob like mass
7 Animals attack on sight
8 Lose all sense of touch (disadvantage on tactile Dexterity checks)
9 Develop vulnerability to metal (any contact with metal deals double damage, or causes 1 damage per round for passive contact)
10 Lose ability to benefit from a short rest
11 Plagued by nightmares; Must make a DC 17 Wisdom save each night to benefit from a long rest
12 Lose half hit dice permanently
13 Reduce Int and Str to 3 permanently
14 Reduce Cha and Dex to 3 permanently
15 Gain Disadvantage on all magic saves
16 One limb transforms into living Black Kyanite; susceptible to spells like Shatter as if an inanimate object
17 Lose ability to eat, can only sustain life with blood
18 Develop incurable lycanthropy
19 Lose ability to speak (either lose voice, or all dialogue is babble)
20 Translucent skin reveals organs; gain disadvantage on Charisma checks but advantage in Intimidation
Examples of Additional Boons Granted by the Black Kyanite:
Flame Control: gain the ability to cast burning hands at will; cannot control while sleeping
Stone Skin: develop skin of pure stone, but unable to “feel” like normal again.
Invisibility: Become permanently invisible, but all clothing and objects remain visible.
Ability Enhancement: Gain +5 points in one ability of choice but lose 5 in another ability (to 20 max).
Flight: gain the ability to fly, but lose the ability to touch the ground (must always hover just above the ground). Falling becomes a non-issue, but sleeping becomes difficult, as does any other act that benefits from being grounded.
Any boon from the DMG, accompanied by an appropriate minor curse of hindrance, is acceptable as well.