This padded armor is covered in mottled blue cracked carapace. While wearing this armor you have resistance to lightning damage. Once per long rest as an action you can plant your feet and begin channeling electrical energy as if concentrating on a spell. For the next minute electricity crackles from your head to your feet. Any creature that grapples you or makes a melee attack against you while you are channeling this energy takes 1d4 Lightning damage. Additionally, as an action you can fire a 1 foot wide 20 foot long line of searing lightning from your mouth. You can stop channeling before the duration ends as a bonus action. If you lose concentration while channeling you take 4d8 lightning damage.
When you fire a beam of lightning each creature in the line must make a Constitution saving throw against your spellcasting DC. If you are not a spellcaster this DC is equal to 8 + your Proficiency + your Constitution modifier. On a failed save, a creature takes 4d8 Lightning damage, on a successful one it takes half that much damage.