Domains: Vengeance, the unforgiven, the long memory of wrongs.
Era of ascension: Golden Age of Man (~150,000 years ago). Cohort: dead. Died: God War & Long Winter (~75,000 years ago), when his worshippers participated more aggressively than any other faction outside Dyos's, and most were dead before the Long Winter formally killed the rest.
Worshipped by: The blood-feud traditions of the Golden Age — clan structures whose accounting of injury crossed generations — and the covert orders that pursued grievances on behalf of polities too institutionally invested in peace to pursue them officially. No living culture maintains his worship. (The worships edge is authored downstream on the worshipper, not here.)
Vaelos sanctioned the war that the polities declared with all the right paperwork. Uzgaruk sanctioned the kind of war that nobody declared: the named injury that would be answered at a time of the avenger's choosing, on terms outside any institution's reach. His doctrine was deliberately unjudicial. A grievance pursued under his rite required no court's sanction, no priest's mediation, no civil law's approval; it required only that the avenger remember correctly, name the offense correctly, and act in proportion to it. The cult kept the memory infrastructure: oral genealogies of wrongs, marked stones at the locations of unresolved injuries, the small specialist orders that helped clan structures pass the accounting from one generation to the next.
The God War was, for his cult, the long-awaited day. The constraints that had held individual reciprocity at clan scale dissolved into open warfare between divine factions, and Uzgaruk's worshippers participated as full combatants, drawing on memory-banks of inter-clan injury that some of them had been waiting four generations to act on. They were correspondingly the most theologically committed of the war's middle phase and the most lethal at close range. They were also the first non-Dyos cohort to burn out: a doctrine of one-action settlement does not sustain a multi-decade war, and within fifteen years most of his trained avengers were dead with their own grievances completed and nobody alive in their lineage to record the completion. The cold finished the rest as a matter of bookkeeping.
Vaelos is the honorable conquest the polities sanctioned. Dyos is sacrifice as theology. Uzgaruk was the personal grudge writ cosmic — the doctrine that a wrong remembered exactly was a wrong half-corrected, and that the other half was a duty.