The Loc Nar
Wonderous Item, Artifact
A glowing green gem, about a foot and a half across, and multifaceted with 20 faces. Th loc nar is a transdimensional entity, existing somewhere on every single plane, including the far realm from which it apparently originates. The loc nar instantly kills any living thing that touches it, reducing their physical form to a jell, then energy, which it absorbs. It also absorbs the souls of any creatures it kills. The loc nar has the power to project the souls of those it has killed, either to raise the dead, or to provide temporary immortality.
The loc nar can glow as bright as a torch, but is also capable of reducng its glow to complete darkness, at which point the gem's true color is revealed to be pitch black with no reflective qualities whatsoever, looking like a featurless hole in space.
The loc nar has an evil will of its own, with no apparent goals than to simply absorb all life. Normally silent and benign, if motivated to act, it can communicate telepathically through speech and visions, hover at alarming speeds, and change in size and weight arbitrarily. When stirred into acting independently, it can cast spells as a 20th level sorcerer.
It gifts temporary immortality to anyone who willingly sacrifices living things to it, and can also resurrect the dead to drag further sacrifices into its reach. The loc nar uses a combination of these powers to manipulate events such that it will ultimately consume everyone who encounters it, even those who sought it out and made sacrifices to it. It has no loyalties and no remorse.
For anyone who is willing to make sacrifices to the being, it is possible to form a pact to utilize its power for magical purposes. (The loc nar counts as a great old one) In this situation, the loc nar will project souls it has captured to drive magical effects requested by its warlock. The loc nar will typically only accept one warlock per plane, and will plot that warlock's defeat if a more suitable agent becomes apparent.
The loc nar is threatened only by gods and immortals who derive their deathlessness from some other source. It dreads and hates any creature that can handle it directly without dying, because it has no way of attacking them itself, while they are potentially capable of harming it without fear. It is constantly scheming to find ways to commit deicide.
Very little motivates the loc nar to act on its own, and it spends the vast majority of its time in an inanimate torpor. It is generally only spurned to animation when in the presence of an immortal or god.
Each instance of the loc nar is bound to only one plane. Crossing planar boundaries with a loc nar causes the two instances to combine into one. A loc nar can move to another plane or demiplane that does not have a second instance of itself without harm. The loc nar can use souls it has absorbed to express a new instance of itself on another plane over the course of 24 hours.
It is possible to melt the loc nar, and this has been done several times in the past, but it simply results in the loc nar taking on a liquid quality rather than a solid one. In this liquid state, any additional material added to the loc nar is incorporated into its mass. The loc nar then takes the shape of whatever it solidifies as, which has resulted in some loc nar instances being cast into the form of idols, weapons, and even structures.
Aside from merging instances of the loc nar across planar boundaries, no known method of destroying it completely has been identified, though the loc nar itself has admitted at least once that there is a way.
Creatures killed by the loc nar find their souls trapped in an infinite empty void, the demiplane contained within the loc nar, along with all the souls of every other creature it has ever absorbed from any plane. When the loc nar uses its powers or casts spells, or when a warlock of the loc nar casts a spell, souls are converted into magical essence and expelled from its demiplane, destroying them completely to power the effect.