A demon from the Abyss
A demon of the Abyss, it’s domains of influence are life, death and dancing. It seems a reasonable spirit and logical and not particularly violent, with it’s bans being surgical implements and cold iron. It may have others but if so, you are unaware of them.
This demon took control of the Cook County Hospital. Other than exuding an aura of power that made all sensitive to it extraordinarily uncomfortable and having various patients, doctors and nurses break into choreographed dancing that quickly turned into a sensation on YouTube, it hadn’t done much before Chiron confronted it, giving it the choice of destruction or banishment. After a short stare-off with Chiron, it relented, allowing itself to be sent hurling back to the Abyss.
You are still unsure how such a powerful demon got into the Material Realm, however.