Drain Force

You attempt to disrupt a creature’s connection to the weave and prevent it from casting spells. 

Chose one creature within range, the target makes a Constitution Saving Throw.  On a failed save the creature suffers 6d6 Necrotic Damage and 1d6 drained spell slots. On a successful save the target suffers Half as much damage and does not have its spell slots drained. Treat the number rolled as the combined spell levels of slots drained starting with the highest spell slot available. For example if you roll a 4 on the d6, but your highest spell slot is 3rd level you would lose one 3rd level spell slot and one 1st level spell slot. If the remaining number is lower than any of the targets remaining spell slots, the target loses no more spell slots.  Unless a special focus is used as the material component (DM's discretion) the magic drained into the focus by the spell is dispersed briefly after it is drained from the target.