Volatile Arcane Bomb

Following Enhancements to your Arcane Orb, it now sunders enemies with Devastating explosions.
You channel your Arcane Orb through your blade into each of your attacks, marking it with glythes and runes to enhance future strikes. 
Once per turn, whenever you hit a creature with an attack that uses a Finess or Light weapon you can mark the target with an Arcane Strike and deal an additional 2D8 Lightning Damage.
When your Arcane Bomb detonates it rips reality apart, When the third Arcane Mark is applied to a creature it triggers the Arcane Bomb dealing 6D6 Lightning and a number of creatures equal to your proficiency bonus within 15ft must make a Wisdom Saving Throw, on a failed save they take 4D6 Necrotic Damage.