Special Experiments Compound key?

[Mr.White The last Methbender]

I've got all the fumium keys and I beat the boss but where the hell do I find they key to the "last" area?

[sascha.petrovitsch]

You have to use the first Fumium key to unlock the last area. This area consists of multiple subareas where every area is locked by a Fumium key lock.

I hope this helps.

[doc]

The locations of all fumium keys is listed in https://steamcommunity.com/sharedfiles/filedetails/?id=2238737078

Construction Bay	33,34
Workshop - Smeltery	60,51	on Assault Guardian (once you can attack it)
Hive			57,54
Hydroponics		36,12
Water Treatment Plant	55,61
Power Plant		33,69