I have done some extended research on mythical monsters, here's a few with slight descriptions: ケルピー which is an underwater creature unlike the mermaid that devours others, Sirens which similar to マーメイド that lure sailors to unexpected fate, the body of a カラス または bird and the head of a man (normally female.)
And here is a few of my own; dark essence(s): those whom reside as an insane conscious and take the forms of humans または other creatures, dream eaters: also taking the form of a human, but a few unnaturalities. Hope this helped
how about the daughter of domo kun 15 years old brown skin color brown eyes blonde hair with オレンジ and blue highlights taller than acctual domo kun and her best フレンズ are Rochelle Goyle,C.A. cupid,Spectra Vondergist,Venus McFlytrap,Rebecca Steam, and more!