Not to be confused with the first game's stabler version.
The Unstable Tesla Coil is an unlockable Rare item in Risk of Rain 2.
Whenever the Coil is active, bouncing lightning is fired twice a second at any nearby enemies, dealing 200% damage to each. The lighting bounces to up to three enemies total per Coil. The Coil toggles activity every 10 seconds, doing nothing when off.
Completing the Macho Challenge unlocks this item.
The activity state can be determined by small zaps of electricity emitting from the item, as well as the icon on the lower left on the HUD.