Cause Bearer of the Heavens to die.
Bearer of the Heavens dies, triggering itself and Gift of Immortality.
Resolve Gift of Immortality's ability, returning Bearer of the Heavens from your graveyard to the battlefield and creating a delayed trigger.
Resolve the Bearer of the Heavens ability, creating another delayed trigger.
At the beginning of the next end step, both delayed triggered abilities go on the stack.
Resolve Gift of Immortality's, returning it from your graveyard to the battlefield attached to Bearer of the Heavens.
Resolve the Bearer of the Heavens ability, destroying all permanents.
Repeat from step 2.

Destroy all permanents at the beginning of each end step

Bearer of the Heavens

Gift of Immortality

Kill Bearer of the Heavens.
Cast Worldgorger Dragon by paying {3}{R}{R}{R}.
When Worldgorger Dragon enters the battlefield, its first ability triggers, exiling all other permanents you control.
At the beginning of your end step, Bearer of the Heaves triggers, destroying all permanents.
When Worldgorger Dragon dies, its second ability triggers, returning all cards exiled with it to the battlefield under their owner's control.

Combos with "Bearer of the Heavens"