Yes, I made a mistake: you have already explored North of Underwaste (where you have found the book of runes). So your goal in Underwaste is to reach the three doors of the extreme West room (beyond the "1" bridge) and to open them to access further.The Bridge area huh and 5 4 1 note?
The "wizard house" is above the rooms of the King, at the south end of the upper bridge.
If you have found the "Life" scroll to the "Death", I think it's allSo there is more in Sunken to dig?
The map I found ...
Have you visited the small "museum" in Flame River? A secret lies there, with the key of the laboratory and above all the special map.
You speak of the door in Crossroads? Have you read something about Aerion Heir Brotherhood?This button door eludes me as it has letters instead of runic symbols and I tried all the variations

You can find a note of a prisoner in the jail of Candles Tower on AHB.
One of the notes from Athanor and the Aerion Grocers notes in book both crash game.
Damned! I have to test this.
This text was in Arcanum: "Deeply connected to Nature, the Fir Bolg associate all important acts with animal figures
During ceremonies , shamans were used to wear bear trophies
They were holding a red orb meant to represent life.
The most important rituals took place at night or in deep caves"
I have no Ruby Key
It's the key to access the upper dome of the bridge house. Perhaps you haven't noticed, in the Perethian library in Aerion how to open the secret door from within? The same object work also in the throne room in the bridge house, and give you the ruby key.
I think you haven't explored some underground sanctuaries like Fir Bolg Sanctuary (under Rock Cave), Life Tower (under Twisted Forest) or not completed them if you haven't more essences. ALL the maps have underground levels, some have two or three different. Also, finding the essences altars or the essence itself is always the most difficult part of each map, as in Sunken the sqeleton/skull puzzle, the riddles in Life Tower, the Fir Bolg stones rituals, etc...
Duncan