1. The Aeterna Map shows the current state of the City of Aeterna. Place Marks of the Ruins on revealed tiles to gradually build the city.
2. When construction is complete, the city opens and its layout matches the finished map. To maximize rewards, cover as many reward rooms as possible and link them to the start.
3. After all Marks of the Ruins are placed, you can still fill gaps with Aeterna Tiles.
4. If your Marks have low completion, you may reset them and re-challenge the previous Ruins of Aeterna to obtain higher-completion Marks.