|“||I looked one more time at the grim group of newly brought prisoners. (...) What hope could they have when all previous expeditions led by knights had failed? There was one difference, however. The group had nothing to lose, only freedom to win. Maybe that would be enough?||”|
— Alarast Sage of the Royal Library of Nothampton 
Mount Grimrock, sometimes called the top of the world , is an extremely high reaching mountain located in the Northern Realms near Thraelm. It is a setting for events of the first Grimrock game. The only way to get to its top is by airship, there is no natural life and the only people that go there are king's guards, each year carrying the strongest prisoners for their last trial inside the mountain.  The trial consists dropping the prisoners into a pit atop the mountain and letting them to their fate - if they are able to descend all the way down, they get their freedom. Alarast of the Royal Library wrote that of several expeditions inside the mountain there was only one person able to survive and come out alive - it was a member of king's well-equipped group of twelve men led by Lord Perel, he escaped after three days by climbing up the pit they came in and died the same day.  Before his death he reported having visions of spinning cogwheel inside the mountain.
The mountain was actually a prison built to be entered from the top by The Order of Sacred Fire, holding The Undying One at its bottom. The mountain disappeared after four brave prisoners passed their trial, descended to the very bottom, defeated The Undying One and escaped.