Tip for their backstory: focus on the actual reason they would attack Piper, and all the events that led up to it.
It’s quite unlikely it would simply happen, since predators and prey and stuff aren’t really a thing in the Monster World. There would have to be some specific reason like an argument or rivalry breaking out.
For the name I’m lost on ideas too
Maaaybe something relating to goats
Because I looked at Epic Mammott to brainstorm and all I can think of is goats.