The Erasure was a cataclysmic period, the specifics of which are nebulous beyond that it was "real bad". Traces of its impact remain in a region now called the Mark of the Erasure, thought uninhabited (and inhospitable) by most. Owing to this, and a wholesale shift in cultural values and practice throughout Hieron after the fact, it is epochal. Though most likely a series of concurrent and only partly related events, the Erasure may have been caused in part by the Heat and the Dark.
The vague nature of the Erasure was partially inspired by the titular cataclysm of The Yawhg.