Empire of Souls
The masterpiece of Brennai’s golem factory, the Eternal Golem was designed as sentient, using Undead souls and their regeneration process as its power source. Undead were shoved into the primordial fire in its chest module.
The purpose of the experiment was to create a golem with regenerative capabilities comparable, or even higher than those of a troll, with none of the weaknesses.
The rampant regeneration process during its activation test proved too much for its creators. Hopelessly trying to regenerate their bodies, the Undead souls continued to draw deeper and deeper from the wellspring of the Shadowfell. After a short while, the Shadowfell energies burst out of the golem, corrupting everything in its wake and turning the golem itself into an Abomination.