you do not have an arm and thus have a disadvantage on any action that would require 2 hands, and you can not cast spells that require 2 arms.
as a bonus action on your turn, you may summon an arm of electricity in its place. you may do this a number of times per long rest equal to 2 x proficiency bonus, and it lasts for 1 minute. while the lightning arm is summoned, it emits bright light for 10ft and dim light for another 20ft, your unarmed strikes deal 1d4 lightning damage, and any spell that does lightning or thunder damage receives a bonus 1d4 to hit and to damage.
when you deal lightning or thunder damage with either a spell or an unarmed strick, you may spend as many charges of the arm as you like to deal an extra 1d6 to you and the person you hit per charge spent.