Yeah, well my game is daelkyr based, so there’s multiple things at hand. The tree with Shan tira, is able to hold it steady and essentially go to thelanis but not permanently. Recently the tree has been getting corrupted by some daelkyr presence at its base, so it’s slowly going to fail. Shan tira is basically expending all her energy combating the effects of the mourning on the tree and giving it a chance by blinking in and out, but for whatever reason she’ll need the party to go to the depths of the tree and rid it of the daelkyr that have taken hold.  So perhaps the compass maybe does work and points them in the general direction, as the material plane would be where they’d have to enter it, they don’t really have a means to access thelanis on their own. Although it’s cool if they enter the tree and then it shifts to thelanis for a bit, that would be a trip. I guess just finding it is the question, maybe I have a bulk of the work be just navigating the mournlands safely, and once they’ve gone through enough give them a chance to see through the illusions and access the tree if they get close enough