: Much later, on Earth, the Arbiter speaks of reclaiming honor for the
: Covenant. He says this during the Great Schism that has split species into
: varied factions with loyalty to different prophets and shipmasters. This
: is the same Covenant that his species, the Sangheili, have ruled over for
: centuries by abusing the skill and labor of those species lower in the
: imperial caste. Thel seemed to want this empire to remain and likely with
: little to better the conditions and interspecies relations of its members.

My interpretation of the statement was that the Covenant was very, very different once. It certainly benefited the Sangheili to be one of the dominant partners - they got to benefit from the San 'Shyuum's technology while getting to do what they really wanted to do, which was be soldiers - but we know that things haven't always been so bad for the lower castes. The Unggoy once had much more freedoms than they had prior to the schism, until tensions with the Kig-yar and the Grunt Rebellions saw them stripped away to stop that happening again. They were on the verge of extinction when the Covenant found them, and without it may have died out. And we know that the Kig-yar were "hired" rather than conscripted. I think the Covenant, by the end, had become a vast, bloated, stagnant bureaucracy with significant mechanisms in place propped up only by tradition and piety, but that Thel would have wanted to strip that away and return to a back-to-basics approach to the Covenant. Which isn't to say he was much of a reformist by human standards, or that he'd even want to create fair and equal conditions for all loyal to him, but compared to people like Jul 'Mdama he's downright conciliatory.

Of course, Broken Circle might make my imagining of a less corrupt, more benign Early Era Covenant a moot point when it comes out.