The Masters of Evil! Moonstone, Whirlwind, Baron Zemo and Titania. Just found this out about Baron Zemo - he always wears that mask because it is glued to his face with Adhesive X - a super-adhesive that could not be dissolved (except years later by somebody named Paste-pot Pete). See, Zemo was a nazi scientist who was so evil and reviled that he wore the mask to conceal his identity. During a fight with Cap, a vat of the stuff got smashed and stuck the hood to his face. There is rich mythology here.