The Seven Ninja Swordsmen of the Mist is an organisation consisting of only the greatest blade wielding shinobi of their generation from Kirigakure. There can only be seven members at a time, hence the name. According to Suigetsu Hozuki, the swords of the Seven Swordsmen are passed down from generation to generation.

This team consists of a the following members:

Jinin Akebino
Chojuro
Kisame Hoshigaki
Mangetsu Hozuki
Kushimaru Kuriarare
Raiga Kurosuki
Zabuza Momochi
Jinpachi Munashi
Ameyuri Ringo
Fuguki Suikazan

During the Fourth Shinobi World War, Kabuto Yakushi used the Impure World Resurrection technique to resurrect the previous generation of the Seven Ninja Swordsmen of the Mist to fight for Akatsuki and Tobi, that generation was the most powerful in Kirigakure’s history. Zabuza being part of the group that attacked the Allied Shinobi Forces Third Division, Gari and Pakura summoned the remaining six to the battlefield. Mangetsu then summoned most of the swords with a scroll, and most of the swordsmen got an advantage against the Third Division, being covered by Zabuza’s Hiding in Mist Technique. By the second day of war however, all members of the previous generation are eventually sealed, and the Impure World Resurrection technique cancelled. Lets thanks our source: Naruto.Wikia.com