Monstrous War-Leech is a uncommon Creature — Leech Horror card from Dominaria United (DMU), collector number 98. Current market price: $0.13 (foil $0.07), TCGplayer market prices via Scryfall.
Kicker {U} (You may pay an additional {U} as you cast this spell.) As this creature enters, if it was kicked, mill four cards. (To mill a card, put the top card of your library into your graveyard.) Monstrous War-Leech's power and toughness are each equal to the greatest mana value among cards in your graveyard.