From Halopedia, the Halo wiki
The 'sKelln is a leathery, winged aerial predator native to Sanghelios, the homeworld of the Sangheili. The 'sKelln are strong and majestic predators, and are capable of astonishing speeds and insatiable appetites. Known to be voracious and cunning, 'sKelln stalk the skies hunting for prey in the mountains of Sanghelios.
In antiquity, the sky-chevaliers would fly on the backs of 'sKelln and use them on hunts. The Uztet'sKelln attack-fighter was based on and named after the animal, with its successors following a similar design. The biomimetic aesthetic of the D'nomlhe-pattern Banshee is considered to bear particular resemblance to the 'sKelln. The Banshees utilized by the Banished have been twisted from their 'sKelln inspiration to closer resemble an aerial predator from the Jiralhanae homeworld of Doisac.
List of appearances