The former royal scientist, Altertale's Asriel is swapped with W. D. Gaster.
Asriel is a mysterious monster who worked for King Papyrus as a Royal Scientist. He was wiped out of existence after falling into the void, but Toriel and a third of his followers seem to remember him.
- Gaster personality prevails over the original Asriel personality.
- Father of Toriel and Asgore.
- Created his children in a lab, although they are biologically his.
- Was 35 at the time of "death".
- Was completely erased from existence, and can only be found by editing the game files.
- He sometimes appears to Toriel, but never says anything. He just stares at her, keeping a horrifying expression on his face.
- Fully aware of the timelines.
- If it were possible to fight him, he would use fireballs, "Orange Heart", Dreemurr Beamers, and a few other attacks neither of his children have possession of.
- Utilizes standard, albeit broken and distorted, text
"Beware of the man who does not exist"
– The Riverperson