Marrow and the Unholy Hoard

As an additional cost to cast Marrow and the Unholy Hoard, you may discard a land card. This spell costs {3} less to cast if you do.
Marrow and the Unholy Hoard's power is equal to the number of Rats you control.
Whenever Marrow and the Unholy Hoard attacks, create two 1/1 black Rat creature tokens that are tapped and attacking.