Antecedent Tumulus

Antecedent Tumulus enters the battlefield
tapped.
When Antecedent Tumulus enters the
battlefield, you may pay {2}. If you do, move
your commander from the command zone to
your graveyard.
{t}, pay 3 life: add two mana of any one color to
your mana pool. Spend this mana only to cast
legendary spells.