Arachnovolt

Spider Climb. The spider can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.

Web Sense. While in contact with a web, the spider knows the exact location of any other creature in contact with the same web.

Web Walker. The spider ignores movement restrictions caused by webbing.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: 6 (2d10 + 3) piercing damage, and the target must make a DC 15 Constitution saving throw, taking 15 (2d10) lightning damage on a failed save, or half as much damage on a successful one.

Web (Recharge 5–6). Ranged Weapon Attack: +5 to hit, range 30/60 ft., one creature. Hit: The target is restrained by webbing. As an action, the restrained target can make a DC 12 Strength check, bursting the webbing on a success. The webbing can also be attacked and destroyed (AC 10; hp 5; vulnerability to fire damage; immunity to bludgeoning, poison, and psychic damage).

Recharge. If Arachnovolt is attacked by lightning or thunder damage it may use a reaction to heal 25 hitpoints.

Siphon. Arachnovolt may steal electricity from anything in a 100 foot radius, giving it 5 temporary hitpoints per day of charge.

Lightning Rod (Recharge 6-8). If Webs are 400 feet above ground level, the webs act as a lightning rod, from there it will then use Lightning Surge. or Recharge. 

Shock Wave (Recharge 6-8). Arachnovolt charges energy and stomps sending a wave of electricity through the floor in a 60 foot radius, everything in range must make a DC 15 Dexterity saving throw, taking 45 (5d10) lightning damage on a failed save, or none on a successful one.