To unlock of all Lego Marvel Super Heroes playable characters, you basically have to finish the Story Mode levels .. Extremis Soldier. Follow the red studs to find the cat, taking out the waves of Extremis soldiers that show up. After a few battles and chases, the cat will finally. Extremis Soldiers - Marvel Cinematic Universe: Extremis was first developed by Dr. Maya Hanson. She later joined A.I.M. and further developed.