Chuck's Charnifexerous Cannon Arm

Arm is replaced with a two fingered insectoid arm that has an embedded biological weapon that fires a acid blast towards an enemy. It has a plus two to spell dc, the target must succeed a constitution saving throw or take 1d12+2 damage, in return they take a -3 to dexterity and charisma.

The spell increases in damage by 1d10 every other level.