The Mycotyrant is a mythic Legendary Creature — Elder Fungus card from The Lost Caverns of Ixalan (LCI), collector number 305. Current market price: $1.84 (foil $2.51), TCGplayer market prices via Scryfall.
Trample The Mycotyrant's power and toughness are each equal to the number of creatures you control that are Fungi and/or Saprolings. At the beginning of your end step, create X 1/1 black Fungus creature tokens with "This token can't block," where X is the number of times you descended this turn. (You descend each time a permanent card is put into your graveyard from anywhere.)