Aetheric Siphon

When you cast this spell choose a target. They must succeed a Constitution save against your spell save DC. If it is a success the spell has no effect. If the save fails then the target loses 1d4 spell slots of a spell level that is half (rounded down to a minimum of 1) of the level Aetheric Siphon was cast at. You then regain a number of spell slots equal to half (rounded down, to a minimum of 1) of the number of slots that were lost by the target.  (Example: If this is cast at third level and you rolled a 4 the target loses 4 first spell slots then you regain 2 First level spells slots)

Additionally, if you were to regain more spell slots than you have the capacity for then you gain temporary spell slots equal to the number of slots siphoned minus the amount to fill up your spell slot maximum for the siphoned spell level. If the temporary spell slots are not used by the time you take a long rest then the extra aether you accumulated will dissipate from your body at the end of the long rest. 

Example: If you have used 1 first level spell slot and then cast this spell and regained 2 first level spell slots, then you regain the fourth spell slot and gain a temporary 5th first level spell slot that lasts until a long rest