Calamity Ganon

is one of the Characters in Breath of the Wild.

Summary
100 years prior to the events of Breath of the Wild, Ganon was sealed in Hyrule Castle. Having ravaged the Hyrule countryside in a grand war, monks banded together to seal away Ganon until a hero was born who could destroy him completely. After the kingdom was all but destroyed, Hyrule fell quickly into chaos and disrepair.

Ganon is currently growing more powerful than ever before, however, and is attempting to break through the castle. He can be scene coalescing above Hyrule Castle in his swarm form, attempting to break the powerful magic holding him in.