Fire Emblem: The Age of Legend
God of Secrets, called the Mad God
Powerful deity first attested to on some shards of pottery from sometime before 1A 1032 as a terrible monster thought to lurk beneath an ancient mountain range.
Later stories recorded by the Third Generation elaborate that “Mad God” Grimholt (literally night god) was seen as a god of secrets and the unknown, a sinister force always lurking on the frontiers of knowledge and civilization. He preyed upon the First Generations for several centuries before being bested by Sekeriah, who reached into the darkness that cloaked him, wrestled Grimholt to the ground, and pinned him until the god surrendered. Rather than killing Grimholt once and for all, Sekeriah extracted tribute from him: Grimholt would forever after lend his power to any human who asked for it in the form of Dark Magic.
This is considered the beginning of Magic, as a discipline accessible to normal humans rather than simply the raw application of massive Quintessence and the will. This tale is paralleled by the later ones of Ehrholt and Skaihalth.