I have gathered from whence the demon was summoned. Regrettably, I fear it's from a particular death dimension known as Hell. Far different from the Helheim that we Asgardians know of. It was easily deduced from the residue left behind that time moved differently. A day of time here equates to years there. Thus the demon essence within you was likely from one of the old ones.
I will not mince words. It will be difficult to trick, and equally so to remove it without one of our number striking a deal with the lord of that realm.
I will work with you and Midgard's mage when you both name the time and the place.