Amberser has always been toyed with by the Goddess of Fate.
His feelings for this ever-present yet unseen Goddess are also very complex.
He had to be grateful for the blessings she sent, which allowed him to survive in this dangerous world through the power of prophecy. If he hadn't become a Diviner Mage, Amberser might have wound up in Hell just a few years after crossing over, becoming fodder on the Blood River Battlefield just like his teacher.
But Amberser equally hated the despair and helplessness brought by fate and wanted to completely break free from it, even if it meant being cursed as a scumbag.
Becoming a Deity was the simplest and most direct way to rebel.