Estua, AEther Strider

Flying, flash
You may cast Estua from exile.
When Estua enters the battlefield, if it was cast from exile, it gains "If a card would be put into a graveyard from anywhere, exile it instead." until end of turn.
At the beginning of your end step, if Estua is in your library or graveyard, you may reveal it. If you do, exile it.