Sword burst of the Hexblade

You start rotating, while your weapon is surrounded by force. You have to make a successful attack roll for each enemies to damage them within 5 feet of you. The damage is always force type. When you reach level 5th, you may make a second attack with your off-hand weapon, or you may add 1d6 force damage to your main hand weapon. At level 11th, you may add 1d6 force damage to your main hand weapon, or 2d6 if single wielded. At level 15th, you may add 2d6 force damage to both main and off-hand weapon damage, or 3d6 if single wielded.

Targets must succeed on a Dexterity savings throw to half the damage. 

You are exhausted till the end of the next round. Any spellcasting or complicated action (based on the DM's judgement) may be failed and maintained concentration is broken, if the hexblade misses its Constitution check. Exhaustion effect will persist till at least one round is not taken without spellcasting or complicated action.