The back door to the Silent City is in the same area where the quest "Sul`Dal Studies" ends up. That is, is in the tunnels accessed from the Bay of Anuk - hope this helps
The final quest to return Anashti Sul to Norrath! If you are grouped with others on the same quest steps, each action should update all appropriate group members.
Head towards the Isle of Mara and zone into The Mystic Lake. From there, head to The Forsaken City located at -263.97, -40.44, 48.86 . Be aware, this is underwater, so you will need to have some form of underwater breathing item to get there. When you're inside the city, head to the Plunderer Base Camp and click the bookcase located at 51.51, -50.83, -26.52 .
Now you have the book, head to the Loping Plains to start killing mobs. You need vampires and ghouls, 12 of each.
The ghouls can be found around -353.74, 30.75, 209.66 and a bit further on at -99.32, 49.59, 142.45 . There are also a large amount of ghouls around -23.32, 48.86, -197.67 .
For vampires, go into Castle Mistmoore and kill the ones at the entrance. These can be a bit tough solo if you're only 70, so consider taking a bit of help. At 80, it's pretty easy. Once you have all 12 updates, head back to Sinking Sands and go to The Silent City backdoor. It's found at -945.53, -228.76, -1047.90 . The instance you want is called "The Empowered Fountain of Life". Select that and zone in.
Once inside, head towards what looks like a moonstone pool in the center of the zone. You can see it from zone-in, and if you really need the loc, it's -0.21, -13.40, -100.88 . Right-click it to perform the rite. Hail the Avatar of the Forgotten to update your quest. She will give you a decanter of blessed Fyr'Un water that you must administer to followers of Rodcet Nife outside Qeynos.
Of course, this means you have to go back to Antonica. Target the follower, use the vessel, then talk to the follower afterwards for the update. The followers can be found in the following locations:
Murgen Stillwhil: -506.63, -14.26, 154.04 (just east of the middle qeynos tower, first person)
Liyah Relltis: -499.48, -0.96, 560.24 (near the claymore, second person)
Gerehmie Lasherig: 375.67, -12.26, 812.25 (near the lighthouse/docks, third person)
Jeizin Faelurn: 139.18, -17.17, 202.86 (around the merchants between the two Qeynos gates, fourth person)
Now you've turned those five people, head to North Qeynos. The heroic guards are 55, so just use the gate and be careful of epics. Head to 473.33, -20.92, -218.69 and talk to Plumetor Dul'Sadma. Once done, head into the Temple of Life and use the portal to get into the heart of it. Inside, click the small orb at -6.28, -4.21, 5.66 . Doing so will cause 3 "defenders of Nife" to spawn. These are ^^, level 75 and heroic, non-aggro but they still attack you immediately. Make sure you take help for this part.
Killing these will update the quest. Return to Plumetor Dul'Sadma outside and talk to her. The quest will update again and she will enter the temple with her undead. Now, return to the Sinking Sands and hail her there. That's it! The quest line is finished and you have your nice, new Cloak of the Forgotten to show for it.
I must now perform the summoning ritual that will provide the pathway for Anashti Sul to return to Norrath. I will need to enter the Forsaken City to collect a tome detailing the ritual I must perform, then carry out whatever tasks the Forgotten Goddess asks when she materializes. Once I have completed this deed, the return of Anashti Sul will be complete.
Stage 1
I must collect the Rites of the Creation Age, a tome within the Forsaken City. I will need to follow its instructions to complete the rite.
Start:
I must collect the tome, the Rites of the Creation Age, which I should be able to find in the Forsaken City.
Complete:
I have found the Rites of the Creation Age.
I have collected the Rites of the Creation Age.
Stage 2
I must collect the blood of those who were given Anashti Sul's gift.
Start:
I must collect blood of those that were borne of the Ewer of Sul'Dae. I should be able to find vampire blood within the lands of the Loping Plains, and within Castle Mistmoore.
Complete:
I have gathered enough of the vampire blood from within Loping Plains.
Start:
I must collect blood of those that were borne of the Ewer of Sul'Dae. I should be able to find ghoul blood within the lands of the Loping Plains.
Complete:
I have collected enough ghoul blood.
I have enough of the blood.
Stage 3
I have everything I need to perform the ritual to summon Anashti Sul back to Norrath.
Start:
I must perform the rite in her ancient temple within the Silent City to summon Anashti Sul.
Complete:
I have summoned the Forgotten Goddess, Anashti Sul.
Start:
I should speak with Anashti Sul and welcome her to Norrath.
Complete:
I have spoken with Anashti Sul, and am now tasked with announcing her return.
I have summoned Anashti Sul, and have received her command to spread her word.
Stage 4
I have been ordered to administer the gift of Anashti Sul by the goddess herself. I must find those she has chosen to receive the gift of blessed Fyr'Un water.
Start:
I must locate recipients for the gift of Anashti Sul, who should all be outside of Qeynos. I should search for one out on a pilgrimage, perhaps along the Qeynos Highway.
Complete:
I have found the first recipient, and have administered the gift.
Start:
I must locate recipients for the gift of Anashti Sul, who should all be outside of Qeynos. A newer member might be out studying monuments important to the history of Qeynos, such as the Qeynos Claymore.
Complete:
I have found the second recipient, and have administered the gift.
Start:
I must locate recipients for the gift of Anashti Sul, who should all be outside of Qeynos. It's likely that one is looking to spread the word of Rodcet Nife beyond Qeynos, so I might do well to check near the docks.
Complete:
I have found the third recipient, and have administered the gift.
Start:
I must locate recipients for the gift of Anashti Sul, who should all be outside of Qeynos. I should search for one preaching to the farmers as they shop for their necessities.
Complete:
I have found the fourth recipient, and have administered the gift.
Start:
I must locate recipients for the gift of Anashti Sul, who should all be outside of Qeynos. I should seek out one who might be spreading the word of Rodcet Nife to weary travelers.
Complete:
I have found the fifth recipient, and have administered the gift.
I have given the gift of Anashti to those that she has chosen. I must now be ready to announce her return.
Stage 5
I must now announce the return of Anashti Sul to the followers of Rodcet Nife.
Start:
I must meet with Plumetor Dul'Sadma in North Qeynos, along the wall near the Temple of Life.
Complete:
I have spoken with Plumetor Dul'Sadma.
Start:
I will need to create a distraction within the heart of the Temple of Life so that Plumetor Dul'Sadma might be able to enter the temple grounds outside.
Complete:
I have created a distraction within the Temple of Life by destroying an artifact within it.
Start:
I must enter the Temple grounds near the Temple of Life and let Plumetor Dul'Sadma know that the way is clear.
Complete:
I have helped announced the return of the Forgotten Goddess to the followers of Rodcet Nife.
I have announced Anashti Sul's return, and have reported my success to Plumetor Dul'Sadma.
Stage 6
I must return to Plumetor Dul'Sadma at the Sinking Sands dock.
Start:
I should return to Plumetor Dul'Sadma at the Sinking Sands dock.
Complete:
I have helped Anashti Sul return to Norrath.
I have spoken with the Prophet of Anashti Sul.
I have performed the ritual, and Anashti Sul once again will bring her gifts of everlasting life to Norrath.