From Halopedia, the Halo wiki
Duraan was colonized by the Sangheili "three generations" prior to 2553, settling along the shores of the seas. Even though the planet was only partially habitable, the relative rarity of even a half-habitable world as well as the planet's wide-open spaces appealed to minor Sangheili clans whose ambitions were constrained by limited access to land on the Sangheili core worlds. During one of Covenant Prelate Tem'Bhetek's many training missions, his CRS-class light cruiser Spear of Light traveled to Duraan, where the planet's unstable star emitted solar interference that caused the cruiser's energy shielding to deplete. The Prelate took note of this, and sought to apply it in the future.
In 2553, the Prelate lured Shipmaster Rtas 'Vadum's CAS-class assault carrier Shadow of Intent to Duraan as part of his trap to enact revenge against the Sangheili. When the carrier arrived in the system, the Prelate had Spear of Light begin bombarding settlements on Duraan. As Shadow of Intent moved to stop the cruiser, Duraan's unstable sun depleted the carrier's shields and disrupted its plasma weaponry. Spear of Light moved close towards Shadow of Intent, and the Prelate led his forces in a boarding mission aboard the carrier in an effort to take Shadow of Intent for himself. However, the Prelate and his Jiralhanae forces were defeated. After 'Vadum put an end to the Prelate's plan, the crew of Shadow of Intent rested and recovered on Duraan.
Duraan is a planet with an arid climate with a mottled, orange-and-brown surface. Duraan, the third planet of five in its system, has a tidally locked orbit around its red dwarf star. As a result, half of the planet is covered in perpetual starlight, while the other half of the world is in a state of constant darkness. On its light side, seas are scattered across the planet's surface, noted to resemble ink blown on parchment.
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