Domains: Fate, oaths, binding promises.
Era of ascension: Golden Age of Man (~170,000 years ago). Cohort: dead. Died: God War & Long Winter (~75,000 years ago), when the followers of every rival daemon began declaring each other's promises null and the binding force that constituted her divinity was annulled from every direction at once. She was the first major Golden-Age casualty — her cult collapsed before the Kajiit eruption.
Worshipped by: Treaty-makers of the Golden Age, the standing courts of arbitration between cities, and the soldier-orders whose vows of fealty were administered by her priests. No living culture maintains her worship. (The worships edge is authored downstream on the worshipper, not here.)
Vassanéth was the personal binding force of the promise itself — what made a sworn word load-bearing, distinct from Romath's institutional law that demanded the word be kept. Her priests administered the oaths that closed treaties between rival polities; her shrines were the only neutral ground where soldier-orders renewed their bonds; her doctrine held that a broken oath was a tear in the substance she was made of. A sufficient number of broken oaths, the texts said, would tear her apart entirely.
The God War tested the theology directly. As factions of rival daemons mobilized, each began declaring its enemies' oaths void, theologically annulled at the source, because the rival's god was illegitimate and therefore could not bind. Inside a decade the practice was universal. Vassanéth went first of the major Golden-Age daemons, before the eruption itself, eaten by simultaneous repudiation from every side; her priesthoods reported her absence from the rites months before Dyos's follower walked up the slope of Kajiit. Romath inherited the wreckage and tried to enforce by office what she had held in substance, and lasted only until the cold finished what the broken promises had begun.
Underneath the repudiation ran a quieter failure. The anchor-vessel rite that gave Vassanéth her hold on the material plane was maintained by Krathokh's priesthood, and as the God War broke those orders her bindings had begun to attenuate before the last oath was even voided. She was dying on two clocks at once.