Hmmmm, shouldn't be, here's the kickstarter pages showing off the lair beneath the phantom forest.

https://www.kickstarter.com/projects/larianstudios/divinity-original-sin/posts/561299
https://www.kickstarter.com/projects/larianstudios/divinity-original-sin/posts/454237

I don't suppose its the source temple within the forest with the puzzles as that's only a single level?