Speak to the Devoted Disciple. She asks you to lead her to safety. Use the Tether to the Disciple to get her to follow you. Follow the catacombs to ( -82, 0, -81 ) /waypoint -82, 0, -81, being attacked at intervals by by several mobs that spawn at your level as well as the remaining original mobs (even if they are gray).
Once you reach the exit the Disciple will vanish, leaving behind a bag on the floor. Search it and receive odd seedpod.
Head to the Sinking Sands again. Find a discarded carpet next to the usual carpet. Use it. It will bring you to the Twin Tears. Head west along the ridge to the huge rock to south-west. You'll find the body of a Devoted Disciple of Disease at the rock ( -250, -90, -875 ) /waypoint -250, -90, -875. The quest will update as you near the body.
Return to Evdokia in Gorowyn
The carpet at the Sinking Sands dock will return you to Gorowyn.
Head east to ( -1070, -50, -240 ) /waypoint -1070, -50, -240, where Meldrida Slate will spawn; follow her to a crumbling tower where she will attack you ( -1250, -65, -195 ) /waypoint -1250, -65, -195. Kill her and loot a mysterious rune stone.
Enter The Graveyard ( -1390, -90, -330 ) /waypoint -1390, -90, -330. When you enter there is a crypt to the right ( 29, -10, 23 ) /waypoint 29, -10, 23; right click on the handle of the door and select "Enter using the rune stone as a key" to enter a Defiled Mausoleum. The quest updates.
Pick up the passage rune stone on top of Sir Glimmon's sarcophagus ( -38, -45, -45 ) /waypoint -38, -45, -45. There is no need to kill anything, although if you walk down the middle of the room or stand there, a disturbed soul at your level will spawn and attack.