Bittybolt

It feeds by pressing its prongs to anything carrying current, a lightning-struck rock, a length of the Tower's old wiring, and drawing it down with a contented hum. Slow to move and slower to flee, it relies on a thick shell and a nasty defensive discharge that it releases the instant something bites it, usually to the biter's lasting regret. Colonies of them cluster around the Tower's grounding points at night, dozens of little glowing spheres pulsing gently in unison, recharging like a nursery of night-lights.