this is an Au where you are a shifter monster (if you didn’t know what a shifter is it’s basically a shapeshifter but instead of not having limits you do as your can change your body it’s just you need a host and you need to kill the host in which you can replace them, and everyone in this Undertale Au knows about this and Alpyus is trying to study shifters as they are fascinating to her but as well dangerous and rare as most of them were whipped out) you can ether kill one of the main characters and become them but risk getting caught dew to the changed behavior or you can just stay in your normal black goo form with eyes all over