Coastal Ruins Gate Key
Catacombs 4 Tridents
Temple of Poseidon Place the 4 Tridents		Cleopatra's Palaces Proper play\ End of Alexandria
The Lost Library Pharos Pillar		Pharos, Temple of Isis Usage of the 4 Beetles Retrieval of Mechanical Scarab
Hall of Demetrius Pharos Knot		Clepatra's Palaces Brief visit 4th Black Beetle
Coastal Ruins End of hub		Pharos, Temple of Isis Placement of the two Pharos' 3 Black Beetles Winding Key

Coastal Ruins is the central level and all the others (Catacombs, Temple Of Poseidon, The Lost Library, Hall Of Demetrius, Pharos, Temple Of Isis) are just around it. There are various doors in Coastal Ruins that you can pass through in order to visit the other levels and come back. The only difficult part is that you cannot open some of them from Coastal Ruins and you have to open them from the mid-levels. But this only if you have forgot something and must return back.

In Costal Ruins, you have to find the Gate Key because it will give you the access to the Catacombs level. After a couple of back-tracks in these two levels, you gain the "actual" access to Catacombs. Your objective there is to find 4 Tridents. You can easily skip to the next level (Temple of Poseidon), but do not do that unless you have found all the Tridents. Then you can proceed to the Temple of Poseidon level. In there, you have to only place the Tridents, because this will open the route for the Lost Library. Your target there is to find the Pharos Pillar (the first of the two componets that will allow you to exit the hub). Once you find it, you can proceed to Hall of Demetrius. This is a small level and Pharos Knot (the second component) is not difficult to find. Once you have it, you can return to Coastal Ruins. Instead of taking the long route back by re-visiting all the past levels, pay attention from where Werner escaped. This will take you to Coastal Ruins directly and it will also give you the access to the level's only Secret. Then you can go to Pharos, Temple of Isis.

In Pharos, Temple of Isis level you place the two components you found and you can proceed. The goal here is to get the Mechanical Scarab and its Winding Key. In order to retrieve the Scarab, you have to find 4 Black Beetles. The first three Beetles are in the current level and the fourth one is located in the next level, Cleopatra's Palaces. So, for just a few minutes, you have to skip to the next level, get the Black Beetle and return back. Once you have the two components (Mechanical Scarab and Winding Key), you can go to the next level (Cleopatra's Palaces) and play properly.