Welp, i was wrong it was a nuckelavee prop for those that got it right. Still, i prefer the original appearance of the nuckelavee.
I feel that little by little Chise's body is assimilating the curse (the dragon one), as a Slay Vega as was said she is close to fae than human in some aspects so it isn't far fetched that her body may do that, she wasn't the intended target of the curse and the dragon likes her so it has that chance because i doubt the curse would give anyone else all those physical enhancements that it gave her.