The Super Soldier Serum is a chemical solution originally developed by German scientist Abraham Erskine. The serum was formulated to enhance the human body and mind, and was utilized by the United States Armed Forces during World War II in order to create the world's most advanced soldiers.
In Marvel: Ultimate Alliance, it is also the name of a piece of equipment the heroes can wear. It is dropped by Dark Captain America upon his defeat within Doom's Castle. When equipped, it raises the wearer's Defense by +9%.