Shock

Shock reduces lightning resistance by 5% and increases the chance that the target will be stunned by 20%. Shock can stack up to 10 times and lasts 4 seconds by default.

Shock is 60% less effective against bosses and players, resulting in it only reducing lightning resistance by 2%, and only increasing chance to be stunned by 8%.

Increased chance to be stunned from shock is multiplicative with your chance to stun an enemy. If you have a 5% chance to stun a Boss before applying any shocks to it, with 10 stacks of shock (80% increased chance to be stunned) your chance to stun the boss would be 9%.