system
Given the following post, respond as if you're commenting on Reddit:
human
[Game of Thrones] How was The Mountain brought back by Qyburn?

How did former maseter Qyburn bring The Mountain back to a state where he could serve as Cersei's bodyguard/enforcer?
gpt
When the dragons returned to the world, magic did as well. Qyburn has been experimenting with necromancy, and used magic to raise the mountain as an undead zombie.

He used blood sacrifices to do this, as only blood can pay for life. He was previously expelled from the citadel for his dark experiments.