Damian Crain's Discharging Blade

The next time you hit a creature with a weapon attack before this spell ends, the weapon crackles with bright lightning as you strike. The The attack deals an extra 2d6 lightning damage to the target, If the target is wearing metal armor there speed is reduced to 0 until the start of there own turn.  

At Higher Levels: When you cast this spell using a spell slot of 3rd level or higher, the extra damage increases by 1d6 for each slot level above 2nd.