Arcane Strikes

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 imbue the target with an Arcane Mark and deal additional damage equal to the Arcane Strike Dice (1D4) or, expend 3 Arcane Marks to unleash an Arcane Bomb (3D6). Any single creature cannot have more than 3 counts of Arcane Marks at one time, if it has 3 or more counts at any point the Bomb Detonates. On the third Strike attack, the Arcane Bomb automatically triggers and the Arcane Strike Damage is converted to Arcane Bomb Damage.

The Arcane damage increases as you gain Spellblade levels.
At 6th level, your Arcane Strike deals 1D6 Lightning Damage and Arcane Bomb deals 3D8 Lightning Damage. At 14th (2D6 and 3D10) and at 18th (2D8 and 6D6).