Zed is the first ninja in 200 years to unlock the ancient, forbidden ways. He defied his clan and master, casting off the balance and discipline that had shackled him all his life. Zed now offers power to those who embrace knowledge of the shadows, and slays those who cling to ignorance.

An orphan, Zed was taken in and trained by a great ninja master. Only one other student appeared to be Zed's equal - the master's son, Shen. It seemed Zed could never win the favor of the master, as every match between the rivals ended in a draw. Frustrated and jealous, he sought an advantage. The young ninja ventured into a sealed part of the clan's temple, where he found an ornate, foreboding box. Sensing the dark knowledge within, Zed knew he should not open it, but he peered inside nonetheless. In an instant, shadows touched his mind, revealing techniques that had long been hidden. Now armed with a secret edge, he challenged Shen, and this time he defeated the master's son. He expected praise and recognition in his moment of victory, but somehow the master knew Zed had used forbidden ways, and banished him.

Humiliated, the young ninja wandered for years. His bitterness turned to ambition, and he began to train others in the style of the shadows. As his power grew, so did his circle of followers, but he knew that without the box, his technique would never be perfect. One day, Zed looked at his followers and saw that his students were now an army. He led them back to the temple to claim his prize. At the gates, he was surprised to find the old master waiting, receiving Zed and his disciples as if they were welcome guests. The old man laid his sword at Zed's feet, declaring that he had failed Zed as his master. By banishing his former student, the master had doomed Zed to the shadows, instead of leading him to the balanced path. The old man implored Zed to enter the temple, destroy the box, and lead his followers to balance. The dark ninja followed the master inside. Moments later, the assembled ninjas heard Zed cry out in pain. Mysteriously, he emerged unscathed, and threw the severed head of the master at Shen's feet. Screaming in rage, Zed commanded his followers to slaughter the master's students and seize the box.

That day, the old ninja order fell. Though many students died, some escaped thanks to Shen's heroic efforts. Now the temple is a dark training ground for the Order of the Shadow. Zed rules as the Order's master, and his edict is simple: perfect one's technique, and kill all ninjas who refuse to embrace the shadows.

''Balance is a lie - we are the true ninjas.''
-Zed

Pros cons
He can easly take carry down you are squishy
easy escape
can be strong early game

Here is a list of items I find essential for Zed to be successful.
youmhuu's ghost blade: it speeds your movement and attack speed for more easier carry kills
Warmogs armor: just for the health héhé
Last whisper: for just being OP
Blade of ruined king: steal movement speed
Maw of malmortirius: for the MR and the extra dmmg on low health

Your tank have to make the teamfight not you otherwise you died and couldn't do anything wait for the tank to engage and try to get their carry down with Death mark.

Don't change the offensive masteries you can defensive masteries to stack them better with your runes: instead of armor you pick the MR master. You are free in that.

They are best for zed/ most of top champs or you can go for full AD