The Arkham Horror Statistics spreadsheet lists one of the ways to awaken the Ancient One as "Opening the gate of Kadath". To date, it has never been achieved and I'm curious about why. I took a look through all of the encounter cards for Unknown Kadath but didn't see any that referenced opening a gate that would awaken the Ancient One.
So how does one open the gate of Kadath and why is it so difficult that it has never been accomplished yet?