Krovikan Rot is a uncommon Instant card from Coldsnap (CSP), collector number 63. Current market price: $0.15 (foil $0.50), TCGplayer market prices via Scryfall.
Destroy target creature with power 2 or less. Recover {1}{B}{B} (When a creature is put into your graveyard from the battlefield, you may pay {1}{B}{B}. If you do, return this card from your graveyard to your hand. Otherwise, exile this card.)