Well this is a little different. This time you have to add your character in UNDERFELL. That means instead of their likely nice personality, they're hardcore mean. You can use any of your characters, but make sure they fit the Underfell status. MOAR UNDERFELL
Credit to @ReturnOfOskar The thing over Eternity's eye is a scar, by the way. It keeps glitching-ish and I can't fix it....but when have I ever cared X3