Zed is a very special high cost Assassin Unit with 0 damaging abilities of his own, but to compensate he has very strong item interactions.
Zed's mechanic is to clone himself with his current set of items. His items are not unique, which mean each clone can trigger its own items. Some recommended items on Zed are: Ionic Spark, Redemption and Guardian Angel.
Repeating Crossbow has an interaction where it can stack without cap, granting infinite amounts of bonus attack speed and bonus critical strike chance, which is very strong when in a 6 Assassin comp.
Deathblade will have the same amount of stacks when it is cloned.
New Ability:Active - Living Lightning: Creates a clone of himself behind his current target. This clone inherits its creator's items, stats, and current health, and can cast Living Shadow. Its mana cost is 50 / 25 / 0 higher.