From Halopedia, the Halo wiki
The Panom keep is a Sangheili keep in the state of Panom on Hesduros. Panom is the elder of the keep and kaidon of the state. In March 2553, Jul 'Mdama teleported to Hesduros from ONI Research Facility Trevelyan, landing in the middle of the portal structure known as the "holy gate" by the locals, surprising a young Sangheili named Rdolo, who went to inform his uncle, Kaidon Panom, who quickly arrived to investigate. After Jul informed them of the Great Schism, the end of the war, the Arbiter's alliance with humans, and the start of the Blooding Years, Panom invited Jul into his keep.
The Servants of the Abiding Truth led by the Pale Blade used the portal in the keep to infiltrate Onyx, forced to leave behind much of their heavy armor behind until they found a bigger portal. 
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