Charged Shot

You summon a ball of shimmering arcane energy and hold it while it charges.  If you lose concentration on the spell, you must make a Dexterity saving throw at disadvantage as the ball of energy explodes in your hand.  On a successful save, you can use a reaction to throw the ball of energy.  Either as a bonus action, or a reaction taken as a result of losing concentration, you can throw the ball of energy, make a ranged spell attack against a target you can see within range.  A creature takes force damage equal to the total accumulated damage.

The spell's base damage is 3d8. If at the end of your turn the ball has not yet been released or detonated, the damage increases by 1d8.