he is a part of the Bad Sans's group (Horror Sans, Dust Sans, Nightmare and Killer) and lead by Nightmare Sans. Nightmare is seemingly cold, and is cold, but Killer finds it cute if anything. He finds Nightmare's tendrils interesting and fun. Killer is also a flirt, and reads people easily and He's a very professional killer, he lies well and plays great, if he's not fussy or flustered.