Thunder belch

You mumble a low moan, and you feel electrical power humming through your body. Green chaotic electrical bolts soar from your mouth. Any creature within the 25 foot cone (starting from you) must make a Con save, or take 6d6 lightning damage. If the creature(‘s) are within 5 feet, they have disadvantage on the Con save. You must also make a Con save, if you fail, you take 1d4+2 lightning damage, as the thunder lashes back with its disorderly nature.

For each level above 3rd, the damage increases by 2d6 per level, but also increases the damage you take (if you fail) by 1d4+2.