Isildur's Fateful Strike is a rare Legendary Instant card from The Lord of the Rings: Tales of Middle-earth (LTR), collector number 91. Current market price: $0.29 (foil $0.48), TCGplayer market prices via Scryfall.
(You may cast a legendary instant only if you control a legendary creature or planeswalker.) Destroy target creature. If its controller has more than four cards in hand, they exile cards from their hand equal to the difference.
All The Lord of the Rings: Tales of Middle-earth cards and prices