The Great Vault

The Great Vault enters the battlefield with 10
unlock counters on it, and at the start of
your end step, you may
remove one of these counters.
When no counters remain, the vault has opened,
it deals 3 damage to any target and
you create a 13/13 eridian horror with trample, discard this card.
{t}add one mana of your commanders colour