Disk of Arnaine

Whenever a card would enter the graveyard,
instead exile it under Disk of Arnaine. (Via either Discard/Destroy/Sacrifice etc.)
You may cast cards exiled under Disk of Arnaine.
When Disk of Arnaine leaves the battlefield,
return all cards exiled under Disk of Arnaine to
their owners graveyards.
{5}{w}{u}{b}, {t}: Exile target player's graveyard until
Disk of Arnaine leaves the battlefield.