Full grown Wither Poltergeist from the mystery egg batch for:

Wither Poltergeists are spirits that can turn completely invisible at will. They roam around until they find a house or building to claim and are highly territorial over this place. They are generally very playful and mischievous creatures that enjoy moving around, knocking over, and hiding small items around the house. Wither Poltergeists have a strange taste for cobwebs and can't resist gobbling up any they find, often causing abandoned houses to look more tidy than expected.

Full information sheet on Wither Poltergeists can be found here: https://www.furaffinity.net/view/20977459/