Crashing Footfalls is a rare Sorcery card from Modern Horizons (MH1), collector number 160. Current market price: $0.49 (foil $3.40), 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.