Coffin Purge

A spell cast using flashback will always be exiled afterward, whether it resolves, is countered, or leaves the stack in some other way.

If a card with flashback is put into your graveyard during your turn, you can cast it if it’s legal to do so before any other player can take any actions.

You can cast a spell using flashback even if it was somehow put into your graveyard without having been cast.