Nahiri's Warcrafting is a rare Sorcery card from March of the Machine Promos (PMOM), collector number 155p. Current market price: $0.34 (foil $0.27), TCGplayer market prices via Scryfall.
Nahiri's Warcrafting deals 5 damage to target creature, planeswalker, or battle. Look at the top X cards of your library, where X is the excess damage dealt this way. You may exile one of those cards. Put the rest on the bottom of your library in a random order. You may play the exiled card this turn.