A single-level lab that unlocks the chance to apply shock to enemies hit by Chain Lightning, which results in enemies receiving more damage.
The chance starts at 2.50% and can be further increased with the Shock Chance lab, and the multiplier starts at 1.10x which can be further increased with the Shock Multiplier lab.
You unlock this lab in Milestones by reaching Tier 7 wave 60.
Chain Lightning Shock - Lab values, costs, and duration (1 level)