Killer Sans is very maniacal, likes killing, hates sparing, and generally is a negative character. He also has major depression. Killer also seems to suffer form multiple personality disorder, as at times (with whatever magic is left) a tiny speck of an eye will appear in his right socket, this is classic sans trying to get out. This is when he'll have little breakdowns and freak out a little, as he's beginning to feel again and he's reminded of the pain he's caused, not only that but he also has a shadow-like papyrus that will sometimes appear to him, this is his guilt going into overdrive as his sins crawl up his spine...