Eugene Victor Tooms. He's a mutant that's over 100 years old. He stays alive by eating the liver of 5 victems every thirty years, using the strange ability to be able to stretch his body out of porportion to aid him. That was till Mulder and Scully came along! ;)But he's not what you're looking for...

"Is there any way I can get it off my fingers quickly without betraying my cool exterior?" -Mulder talking about the bile on his fingers