- last post: 01.01.0001 12:00 AM PDT
If you read the books, there are many Forerunner artifacts that both Covenant and Humans have found, mainly Covenant though. On these artifacts, there is cryptic writing, like heiroglyphics that are believed to be star maps or directions. That's how they found Reach, when on Reach, they went straight for the museum which had a forerunner artifact. I believe Cortana analyzed one of the artifacts and found the directions to Reach on it, she also found some to Earth I think. That's why Regret went there at the beginning at H2 but didn't know it was our homeworld.