Super-Soldier Serum is a rare Enchantment — Aura card from Marvel Super Heroes (MSH), collector number 299. Current market price: $0.97 (foil $1.38), TCGplayer market prices via Scryfall.
Enchant creature Enchanted creature gets +2/+2, has first strike and vigilance, and is a legendary Soldier in addition to its other types. Whenever enchanted creature attacks or blocks, attach any number of target Equipment you control to it.