Full Name: Osoyo, the Blackfrost Whale
Osoyo was once a great threat, to the point that information about it is restricted.
In Session 022 we spoke to Jenthiel’s mother:
His imprint was on the Shadewither Key and seemed to be the origin of the Obnubilate Curse that was placed upon it, though the imprint itself was rather incomplete and the key itself did not want this on it. The imprint is likely tied to the curse itself, as well as something else that happened on Golarion - we think perhaps she meant The Missing Moment.
She further explains:
Millennia ago Osoyo was near the ancient homeland of Silverian, in a vast canyon-filled sea of mist. The ice-blue whale drifted through the air as if a fish in water. Those that encountered it and inhaled the vapor grew powers, but also became enthralled by the whale. THe high elfin families subdied it at great cost, and shackled it to the Crown of the World. It lays sealed below the thickest of ice caps on Golarion.