1. The Aeterna Map displays the current status of the City of Aeterna. You need to place Marks of the Ruins on revealed areas of the map to progressively complete the construction of the City of Aeterna.
2. Once the construction is complete, the City of Aeterna becomes accessible to you, and its terrain will match the completed Aeterna Map. Therefore, when constructing it, aim to cover as many reward rooms as possible and connect them to the starting point to maximize your rewards.
3. After all Marks of the Ruins have been placed, you can still fill the map with Aeterna Tiles.
4. If the degree of completion of Marks of the Ruins isn't sufficient, you can choose to reset them. You can then challenge the previous Ruins of Aeterna again to try and obtain more complete Marks of the Ruins.