Ur-gold is the scattered essence of a dead god, and the most sacred substance known to the Fyreslayers. When Grimnir, the duardin god of battle, destroyed the godbeast Vulcatrix in a cataclysmic duel, both were annihilated, and the warrior god's shattered divinity rained across the Mortal Realms as motes of golden metal fused with ordinary ore.
The Fyreslayers, Grimnir's fanatical descendants, believe every fleck of ur-gold holds a spark of their god, and their entire civilisation is organised around recovering it. This is why they famously fight as mercenaries: they demand payment in gold not from greed but from faith, since any hoard might conceal traces of their sundered deity. Runesmiters and runemasters test each haul with ritual care, and true ur-gold is worked into runes that are hammered directly into a warrior's flesh.
These runes are the source of the Fyreslayers' power. When roused in battle they blaze with inner heat, lending the berserkers superhuman strength, speed, and resilience, and the mightiest heroes go to war studded with them. Every rune spent in battle also edges the lodges closer to their great hope: that when enough ur-gold is gathered, Grimnir himself might one day be reforged from the fragments his children have so faithfully collected.