You bless a creature of your choice with  the peace and joy that is Uniformity.   Before the spell ends, whenever the target makes a 1d20 roll,  the target must make an normal WIS saving throw.  If he fails the saving throw he is required to substitute the 1d20 with a (2d20/2) roll, and the spell continues until the next 1d20 roll where he has to check again.  If the target makes it's saving throw then the target rolls the 1d20 as usual and the spell ends early. The target can choose to voluntarily fail the WIS saving throw if he so chooses.

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the target must substitute the 1d20 with a ((spell slot level)d20/(spell slot level). Example: when cast at a 6th level slot the target would have to substitute the 1d20s with 6d20/6.