Tier 1 - Stunned enemies generate an electric field dealing electric damage to self and nearby enemies.
Tier 2 - Increase stun duration to 4 seconds.
Tier 3 - Double the electric field damage
Tier 4 - Special enemies can be stunned
Tier 5 - On stun, arcs of electricity jump and spread the stun to 3 nearby enemies (30 second cooldown)