NOTE: This is not the role of Sans or Papyrus. UnderScratch is a tale of Frisk so suddenly messing up the timeline, and finding a way to fix it. This is the design for myself in Underscratch. I proposed myself not to replace any main role (EG: Sans or Papyrus) but to have another reason why this character is here. Hyper (me) is a humanoid monster that highly resembles a tank from the well-known game, diep.io. Hyper can take off his barrel at any time, revealing a white smile under it. Hyper almost always wears a coat, considering he lives in a Snowy place. On a genocide run, Hyper actually follows the player all the way to (insert hotland replacement) to keep an eye on what is going on. Hyper then confronts the player after (possibly) (mettaton replacement) NEO is defeated. A battle starts, and the attacks are tricky to dodge. However, there is an option to spare Hyper and completely abort the genocide run. However, he is not the final boss. On the Neutral/pacifist route, Hyper is first seen in the (Snowdin replacement) town, and decides to battle Frisk, thinking they are a threat. Once Hyper is spared, the player has the option to go to his house and begin a 'hangout'. If Hyper is killed, he throws his barrel at the player, leaving them at 1 HP, before dying in-battle. Hyper's real reason to be in the game is to serve as a part of the royal guard, but also help the player in times of need. Maybe by distracting Antagonists, or giving good advice.
Credit to myself for the sprites.