The Mortisanctum of Yosarum

The freezing air grew colder. The wind whipped and stung Dyson's cracked skin. The labyrinth opened, and Dyson found himself at the Mortisanctum at last, the center of Yosarum's domain. Before him was the god itself. Yosarum hung in the air in an infinite pit, a colossal octahedron thousands of feet long. Dyson's flesh peeled from his frame, and he heard the voice of God directly.
"You stand before Me. Few have passed this trial." The edges of Yosarum’s form split open. "Swear yourself to everlasting service, and I will grant thee a boon."
"I swear", Dyson shivered. Tendrils of Yosarum’s darkness wrapped around him, flaying where it touched.
"What do you desire?"
"The ultimate. Knowledge to wield the greatest magic." Dyson spoke between screams of agony.
"It will be yours. But first, suffer the punishment for intrusion."