Once the Champion returns with the Great Sigil Stone, Martin will prepare for the ritual to open a portal to Gaiar Alata - Mankar Camoran's Paradise. The Champion will be asked to prepare and talk to Martin when he is ready. You are given the opportunity to walk freely inside the Bruma stronghold at this point, however there is very little for a player to do beside manage the Champion's inventory. The Champion is unable to interact with anyone besides Martin. Once speaking to Martin again, he will start the ritual and wish the Champion luck.
"Paradise"
Camoran taunts you in his little fun house
After the ritual, the Champion is transported to Camoran's Paradise. It is a small, single level map, with merely two Mythic Dawn agents. All a player must do is effortlessly navigate the winding path to Camoran's Palace to the west.
The Face Off
Upon the Champion's arrival, Camoran will explain that it is too late for Tamriel and that Mehrunes Dagon's arrival into Tamriel is inevitable. The Champion must then face him. Upon defeating Camoran, the quest will end and the Champion wil be returned to Bruma with the Amulet of Kings.
Notes
Preparations for this quest should be made before starting The Great Gate as you will not be able to save or shop between these quests.
For reasons unknown, there is a random civilian inside the Bruma Stronghold whom you cannot talk to.