The strange space through which Fey portals travel.
All that anybody really knows is that’s where the gods live, and it is… not a safe place. Of the gods, DagonDagon is, to put it bluntly, a god. From the Void, he's an ocean-dwelling being with the patience of ancient... More isn’t too bad, at least for those with magic, but pure humans tend to go mad if too long in his presence… and he’s actively trying not to do harm.
There are other gods in that place who have no desire to be so kind.