Tempus Irae seriously starts to troll us with locked doors. At least we have the Sistene Chapel to look at.
We're starting a new Marathon adventure-- this time fighting the Pfhor in Italy of the past in third party scenario Tempus Irae!
Tempus Irae can be played, like the other Marathon games, using the open source Aleph One engine which you can get here for Windows, Mac and Linux:
Tempus Irae and other third party scenarios for the Aleph One engine can be downloaded here: