Lurivium

Most of the ancient AIs still operating on Plavithen have diversified their power systems in order to stay active as the centuries have ticked by and their access to refined fuel sources has dropped off. The fact that most of them are specifically confined by their programming to certain narrow geographic areas has kept them from simply replacing the mining and refining processes that once fueled them with automated versions. Wind, solar, geothermal, hydroelectric and other more esoteric solutions have been set up to keep the AI complexes online.
However, a few of the AIs and most of the ancient containment vaults run on an entirely different power source, namely Lurivium. In addition to being an excellent power source, Lurivium is also the source of aelglurn (and pitgran), as the reactors that run off of it produce aelglurn as a byproduct.
Lurivium is almost preposterously efficient. Most of the AIs that have been running on it for eons started out with roughly a single semi trailer's worth and still have not exhausted their supply. In addition to this, it is stable and not dangerous to be around. Lurivium is not toxic to any species native to the universe that Plavithen resides in, is not radioactive, and is not particularly flammable, electrically-conductive, or explosive. It is an unremarkable pale gray stone, easily mistaken for countless other rocks.
It is also the direct remnants of creation. Doha's Anchor is a massive chunk of Lurivium, and smaller pieces of it serve as anchors to holy sites and safe zones all over the world. It only works in this capacity when it is allowed to sit for some length of time, but the shackled horrors cannot touch it, and using it as a fuel source turns it into something else, negating its protective power.

Type

Ore/Mineral