Slimy Piper is a common Creature — Fungus Bard card from Foundations Jumpstart (J25), collector number 25. Current market price: $0.30, TCGplayer market prices via Scryfall.
Whenever this creature attacks, it gets +1/+1 until end of turn. If you control four or more creatures, it gets +2/+2 and gains indestructible until end of turn instead. (Damage and effects that say "destroy" don't destroy it.)