Around 2776 SD, while the Neferati raised Tarkhetan on the Needle, a procession of priests carried fire north out of Yaif. They drew it from the Flame of First Fire, oldest of the Eternal Flames, and they brought it the length of the peninsula and across the strait without once letting it die. In a cathedral at the new city's center they set it down. That fire is the Evertorch, and it has not gone out since.
The priesthood did not give the fire away. They lent it. Before the first ember left the Temple of First Fire, the founders swore terms to the priests of Origins in exchange for it, and Yaif's Archive of Ashes recorded them in fire on treated stone: who carried the flame, and what the city owed for the loan. Those records still exist. They are exact.
Let it be written who said yes, and in whose hearing, so that no one after can claim the words were never spoken. — from the lending-record, Archive of Ashes, Yaif
What the city owed was not gold. The fire remained Yaif's, held in trust at Tarkhetan rather than surrendered to it, and the terms bound whoever ruled the city to honor the lending: a standing place at the flame for Yaif's priests, an acknowledged rent on the light, and the priesthood's right to call the fire home should it ever choose to. The founders were fire-blooded themselves, and they made these promises easily. They were promising them to their own.
Three centuries thinned the founding line into humanity, and at the Severance the throne passed to rulers who had never sworn the terms and did not hold themselves bound by them. The priests of Origins were turned out of the cathedral. The rent went unpaid, then was reframed as a gift that had never been owed. No emperor has formally refused the lending; none has kept it either. The Kingdoms of Fire date their grievance to this loan and not to the Severance that came after it. By their reckoning the fire in Tarkhetan is still on loan, the debt is still open, and Yaif has not yet chosen to call it home.