MechaTale is an AU containing mostly robotic creatures. Most of the Underground's monsters have been turned into cyborgs or mechs by Alphys and Sans, who pit them against each other to see which designs work well, and which ones don't work so well.
The Underground is basically a robot fight club, run by Sans and Alphys.
Robots/Mechs Created by Sans
Mecha!Mettaton VER. 2
Robots/Mechs Created by Alphys
Mecha!Napstablook VER. 2
Monsters that aren't Robots/Mechs
- Napstablook (Despite there being a Mecha Version of him, he himself is not a mech)
- Gaster (Unconfirmed)