Shadow Titan:

meyerm:

I noticed in the terminal on the last level in Halo 3 The Didact is talking to the librarian about "The great journey" but they were talking about death of all. Is it possible that the prophets and elites read these terminals and misread what they really meant?

It's a possibility, but I think the covenant found forunner artifacts and believed them to belong to the gods, the forunner. Eventually they found a monitor, who said something about the great journy and the halo's and that's how I think it worked

1.No,The terminals where on the Ark and the Secound installation 4. Which was discovered millennium's  after the covenant was formed.

2.They didn't find a Monitor "Oracle" until halo 2 (when guilty spark was captured)

prestongilstrap:

The Covenant mistranslated a specific rune on the forerunner artifacts. I don't know which one or when but I spent an hour or so on the Halo Wiki

Mistranslated the word, more like Misunderstood.

The prophets found the forerunner dreadnought and correctly assumed that their had been a race prior to them that was extremely powerful.

They then made a covenant with the Elites. The prophets find more relics while the Elites protect them.

When Mendicant bias speaks on the dreadnought, the prophets thing the best way to keep the secret that the forerunners (or their descendants) are still alive, is to start a genocidal war with the humans.

Thats the gist of it.