Sans is a Skelington; he has a little brother named Papyrus. Some have argued that Sans and Papyrus have a father named< W.D Gaster. I’m say, yes, he is, but in theory. W.D Gaster made Sans and Papyrus, but through machines, Sans´s test name was 5AN5. After the death of W.D. Gaster, Sans´s name was switched to what we know now as Sans.  If you go to Alpha’s lab and look at Sans’s file, you will see there is nothing documented, but there are signs that he worked in the lab for a period of time as the royal scientist. Sans has the abilities  (gravity, bone summoning, lazers, and gaster blasters). He has 1hp and in 1 attack; he is a major character in Undertale. He first appears in Snowdin Forest, somewhere outside of the ruins. He is the final boss in the Genoside Run. Cu73eonstantly in the Genoside Run, he has to watch his brother die again and again, non-stop after every Genoside Reset, this made him have no care for anything that may happen in the future because he knows the human (frisk) will just reset all over again, but when you kill his brother…  well… let’s just say it’s not pretty, and he will come after you. The rest is happening, even now.