In the Mars Core level, you enter the Lost City of Hebeth at the end before taking the slipgate to Sentinel Prime. Here is its Codex entry:   "Amidst the long and enduring history of Sentinel civilization, there are moments in antiquity that have become buried in time – forgotten chapters that remain concealed to Sentinel historians, waiting to be unearthed. The fallen city of Hebeth is one such tale, all but forgotten to the tomes of legacies past. Once a prosperous port city – a prou