Mirror March is a rare Enchantment card from Ravnica Allegiance (RNA), collector number 108. Current market price: $1.87 (foil $2.79), TCGplayer market prices via Scryfall.
Whenever a nontoken creature you control enters, flip a coin until you lose a flip. For each flip you won, create a token that's a copy of that creature. Those tokens gain haste. Exile them at the beginning of the next end step.