Larian Studios Forums Divinity: Original Sin 2 Divinity - Original Sin 2 - Help/Tips/Tricks Academy - Teachers' Hall - northern hidden area

This is not the door to the south with the portal but there's an area to the east on the map apparently not connected to anywhere else that itself has a door to another area (not depicted on the map). Is there a way in there? Is it possibly a back entrance that I've never found (I've read of one that bypassed the lunar gate puzzle; a hidden hole, I think) but it may be something else entirely. From what I can see, it doesn't appear to be anything interesting back there but, you never know.

Yes. There is 100% a back door into the academy. There is also an achievement for finding it. Less than 12% of people have found it. To find it involves investigating south of the Temple to Duna. You will need some way to get across lava : Teleport, Tactical Retreat, Spread Your Wings, Cloak and Dagger. Once one character is a across you can use the pyramids to get the rest there. There are several places to get across, so it may take a couple hops to get to the correct one of the land masses. The back door to the academy is the only easter egg I have found in that area, but it was worth the search.