The Obverse was "a mysterious region in which Time and Space are not only not one, but never have been and never will be." It operated on different rules from the usual universe, which made it potentially very valuable to the people of that universe. Within the Obverse, at the point where it met the universe, was a space called the Enclave. It was from there that Daedalus spread his Corridors into the universe, connecting worlds the worlds of the universe with those in the Enclave and starting a War.
Although at times she claimed otherwise, the Obverse was evidently the home of Iris Wildthyme. She lived there in the northeast of England, in a basement flat next door to a woman named Sally. (PROSE: The Blue Angel)