From Halopedia, the Halo wiki
The raider is a class of Kig-Yar vessel. They were mentioned as being the closest thing the Kig-Yar have to a true fleet ship. Before the Kig-Yar joined the Covenant, they used refitted raiders to fight off the Covenant from their system's asteroid belts.
Like all vessels built by the Kig-Yar, raiders are less elegant in design than most Covenant ships, mostly consisting of girders, thrusters, and various modules joined together around the ship's central hull. Raiders are strictly space vessels, and can not operate in a planet's atmosphere.
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