Scientist K-124-D is a strange being that comes from a different Timeline. He hides out in most of the War watching and probably studying and maybe even planning. He is somewhat of a Cyborg creature in mechanical body which takes other animals parts and uses them as replacement parts. He has a disturbing interest in War itself and tells of the Juggernaut Wars, a Dimension wide war over a mysterious power called Seriphia Force and a War over domination of all realities. He seems to be an expert in keeping his life secret and once got a run in with Sans. He stalked him for sometime before disappearing back to where he is stationed at. Scientist K-124-D is not Monster or Human but is something else...
His true form inside his "shell" is unknown.
Scientist K-124-D exhibits emotions of Narcissism. He is also very Sadistic and takes pleasure in seeing what Monsters tick. He also seems to have an intense form of Xenophobic hatred for other creatures. He also carries no Male nor Female psyche and is presumably gender-less. He also seems to take some form of satisfaction in the death of other animals save for his own race. He has no pity nor mercy. He even has a since of style by taking animal skins and wearing them...
Scientist K-124-D's origin in how he had arrived in the UnderWar Universe still remains unknown. He seems to be solely on studying the War and seems be only here for that. His next move remains shrouded in mystery. But he seems to make his presence announced when people start randomly seeing graffiti on the walls reading: EXTERMINATE!