Crashing Footfalls is a rare Sorcery card from Mystery Booster 2 (MB2), collector number 204. Current market price: $0.52 (foil $9.08), TCGplayer market prices via Scryfall.
Suspend 4—{G} (Rather than cast this card from your hand, pay {G} and exile it with four time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.) Create two 4/4 green Rhino creature tokens with trample.