It's a magician's hatbug! Hehe. Sorry I didn't have a lot of time to work out some supporting material. You can look at my earlier draft here
, which explains some of the abilities and attacks it can do. It can shoot magical dusts out of its hat hole, which can perform a variety of tasks. One of these can be a tricky gas that confuses the opponent into thinking it is a different Pokemon (Illusion). Its hat armor is also very flimsy (Weak Armor), but when taken off, the hatbug can travel very quickly without its weight.
Anatomically, it has the ability to hide its claws and glowing antennae within the recesses of its hat structure. It can also move those body parts around at will within the hat (as you can see in the WIP art).