Zeed is an evil crime syndicate that deals in kidnapping, terrorism and stealing weapons, and is the main antagonistic faction in the Shinobi series.
In the original arcade game, Zeed was responsible for the kidnapping of children from the Oboro clan, and Joe Musashi was tasked with rescuing them from their evil captors and terminating the Masked Ninja that led Zeed from behind the scenes. After defeating the Masked Ninja, whose true identity is that of Musashi's original mentor Nakahara, it is explained that Zeed was formed with the goal to bring back the Feudal Era of Japan, in which ninja were at their most active during the constant civil wars that took place.
In The Revenge of Shinobi, which took place three years after the original events of Shinobi, Zeed regathered under a new name, Neo Zeed. Seeking to destroy those who would use the power of stealth against them, Neo Zeed attacked the Oboro clan and killed many of their numbers, including their current master. Joe Musashi was unable to prevent the attack and learned too late from his dying master that Neo Zeed had also kidnapped his fiancee Naoko. Musashi journeyed to avenge his fallen clan, destroy Neo Zeed, and reclaim Naoko from their leader, the Ninja Master.
Neo Zeed returned once more in Shinobi III: Return of the Ninja Master, seemingly more powerful than ever with high-tech weapons, deadly robots, and fearsome biological creatures at their fingertips. Most dangerous of all was their new leader, the Shadow Master, a mechanical warrior with abilities equal to Musashi's and weapons of incredible power. Unstopped by the overwhelming odds, Musashi set out once more to destroy Neo Zeed forever.