"Well, that's a long and complicated story. Short version is that where I'm from, most of the population died from a disease that ruptured their organs and had them spewing blood everywhere. I was one of the 10 percent or so that didn't die. Among the survivors were a group called carriers, where the virus had mutated in them and changed their genetic code to allow them to perform superhuman acts of strength and skill, like what I did. Grow body armor, spit acid, lose your physical shape, changing your face into the perfect replica of another's, all sorts of crazy shit. Mine was obtaining another sentient being living in me, that could copy any ability and combine it with others. The downside to this is that if I give someone else a blood transplant, or there's any sort of exchange of fluids between us, they get infected with the virus. Most of the time, the virus would turn them stark raving mad and have them trying to kill everyone they know except myself."