Crystalline Blade

You weave together crystals that imbue a melee weapon of your choice that surround the weapon. This lasts until it hits a creature or until the spell ends. When it hits a creature the crystals shatter into the target lowers the AC of the target by 2 which lasts until it is hit again or for 1 minute otherwise the crystals fade from the target. The components are consumed with the spell

At Higher Levels. When you cast this spell using a 4th spell slot the AC decreases by 3. When you cast it using a 6th level spell slot, the AC decreases by 4. When you cast it using a spell slot of 8th level or higher, the AC decreases by 5.