Will Weakens

You siphon the fortitude out of a creature's mind and sap their mental acuity. The target must make an intelligence saving throw. On a failed save their intelligence, charisma, or wisdom score (your choice) score reduced by an amount equal to your spellcasting ability modifier, taking only half the reduction on a successful save. This spell cannot reduce any of the target's ability scores below 1. This reduction lasts until they gain magical healing from a spell of a level equal to or greater than the level you cast this spell at.

At higher levels. When you cast this  spell using a spell slot of 4th level or higher the score reduction increases by 1 for every slot level above third.