Shang-Chi, Martial Mentor is a rare Legendary Creature — Human Warrior Hero card from Marvel Super Heroes Commander (MSC), collector number 732. Current market price: $0.69 (foil $2.60), TCGplayer market prices via Scryfall.
If one or more +1/+1 counters would be put on a creature you control, twice that many +1/+1 counters are put on that creature instead. Power-up — {5}{G}{G}: Put three +1/+1 counters on Shang-Chi. (Activate each power-up ability only once. Reduce the cost by his mana cost if he entered this turn.)