Start with Quellious in Plane of Tranquility, say 'discreet' to get the task "Into the Temple" (can be done as a group). All you need to do is zone in to Plane of Health and then Demiplane of Life to find Mayor Salvador West. Go back Plane of Health and tell Neelo Leafwind 'passage' to get the solo task "Seal of Approval". Run around and hail the 6 npcs then return to Neelo to complete the task. Back to the Mayor in Demiplane of Life and say 'allow' to get a shared mission "Into the Temple". Zone in by clicking the skull on the desk. Kill mobs, loot and read two scrolls, pick up a third scroll ground spawn, and loot a mirror fragment from a Bokon. Give all four items to the Avatar of Tranquility at zone in to complete the mission and get currency, xp, and the Mirror Fragment of Anashti Sul. This flags you for access to Demiplane of Decay and Crypt of Decay.

Next you need to complete 4 instances 6 times each:

In addition to that you will need to complete all tasks and instances in Plane of Health, Demiplane of Life, Demiplane of Decay, and the Crypt of Decay. This will flag you to be able to requests the tasks and instances inside Crypt of Sul.