Gem of Storm's Eye

Hitting an enemy puts a mark on them for 5 s. Hitting a marked enemy sends a lightning bolt to another marked enemy, dealing 4 damage. The attack can chain to more marked enemies.

After lightning triggers, the effect has a 1 s cooldown before it can retrigger from the same enemy. After the cooldown, the mark is refreshed. The value 4 is a base value that scales with the weapon's level.