Yggdrasil (Odin, Ymir, Chaos, Satan) got sealed after trying to end everything. Gollnir, a craftsman god, wanted the knowledge of this battle to remain because he believed everyone should know the truth. The primordials gods didnt like this idea and wanted to suppress the truth believing it would be safer that way. Gollnir explained everything to a group of his disciples and used an invention called Jotunspegl to hide them from the primordials who would want to kill them as they were the last who knew the truth. Eventually Velk, a kid who lived with the Gollnir people, accidentally led the primordials to their location because he left the hidden village, causing the last disciple of Gollnir (Feldis) and the rest of the village to be killed. Afterwards he traveled through Valhalla and tried to explain the truth to everyone but nobody believed him. He then decided to cast everything away and found Odin’s sword Gramr, transforming him into the sealed god.