By King's Decree

The wielder of Excalibur targets a single creature within range. When casted on the creature they must roll a d20 without any modifiers. If the creature rolls an 18 or higher, they are unaffected by this spell for one hour. On failure to roll above 18, the creature is immediately stricken to vulnerability to everything for one minute disregarding any and all immunities and resistances they may have had. This bypasses Unfaltering Immunities.