From Halopedia, the Halo wiki
A velithra is a large animal native to northern Yermo on Sanghelios, the Sangheili homeworld. The velithra have been domesticated by the Sangheili and used as beasts of burden. They are forced up narrow mountain paths, shortly before a rain season. They are trained to move slowly and one at a time to prevent them from falling off the side of a mountain. The Sangheili have developed a saying based on the animal's patient, single-file trek, meaning that they should only worry about their current priority.
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