Banish is the celestial spirit, unaware of its true and former nature, bound to a greatsword. It was created to defeat The Cannibal King by imprisoning him within the Old Rossashus Cemetery Barrow. The wards on the barrow were weakened by the Evergloom Cult during the events of Malediction Exhumed.
The containment was only truly broken when Calyn Omarion removed Banish from the centre of the barrow standing stones.
Part of the cursed nature of Banish was transferred to Calyn Omarion and Gideon von Scholtz II. Iskar Jarak attuned with Banish the Greatsword.