Sheltering Ancient is a uncommon Creature — Treefolk card from The List (PLST), collector number CSP-121. Current market price: — (foil $1.76), TCGplayer market prices via Scryfall.
Trample Cumulative upkeep—Put a +1/+1 counter on a creature an opponent controls. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)