boss 23 - call of house hardabar - tannhauser trials (tannhauser stronghold basement) 

Call of House Hardabar (Grimrock 2 MOD). Difficulty: Hard.
Download: www.nexusmods.com/legendofgrimrock2/mods/167
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It is essential to install the 4GB Patch to prevent the game from crashing (this happens in large mods for technical optimisation reasons):
Link: www.ntcore.com/4gb-patch/
Download the program, run it, then it will ask for a path, then choose the path where the grimrock 2 executable is: "grimrock2.exe".