Energy Gather/Release

Your body naturally stores remnant magical energy as you manifest spells.  This wild energy is leftover magic from normal inefficiencies in spellcasting, and will release itself once a spellcaster with this unique property runs out of normal spell energy to safely contain it around them.

• Add 1 to your Constitution score.
• Upon using your final spell or pact slot, all creatures within 30ft. of you must make a Constitution save or take 1d12 Force damage, half that if the save is made.
• Resets once at least 2 slots are expended, and no more remain, since the last triggering of this ability.