Filth is a uncommon Creature — Incarnation card from The List (PLST), collector number JUD-66. Current market price: $4.49, TCGplayer market prices via Scryfall.
Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.) As long as this card is in your graveyard and you control a Swamp, creatures you control have swampwalk.