The door to enter the special zone for this quest, Endless Catacombs, is located inside of the Tower of the Four Winds, on the first floor (under the stairs), at ( 28, 36, -162 ) /waypoint 27.5, 36, -161.5.
Due to a bug in the game, you may be able to click on the entrance to Endless Catacombs from outside (The Tower of Four Winds) building without completing quest, Access to the Tower, and its prerequisites. To try this, go to the left side of the building and scroll your camera out to click on the access point. The access point to the Endless Catacombs is inside the tower to the left underneath a staircase. Position your character just outside and to the left of the entrance to the tower. Zoom the camera out as far as possible. Move the camera and your character until you can see to click the Endless Catacombs access point. It takes some trial and error, but as of May 2019 is possible.
The zone has Heroic mobs that scale to at least 10 levels above your adventure level; don't panic, you'll receive a special item to incapacitate them.
Though the wording of the journal makes it sound like this is a timed quest (to get relics before the monks destroy them) there is no rush. See the time saving tips for a quicker way to complete this though.
When you enter the Endless Catacombs, pay attention to the blue-black blob off to the side right in the first room; it's not a monster, it's the exit.
Collect 45 terracotta warriors (the Heroic mobs in the zone) before the monks in the labyrinth's lower passage destroy them in their training.
As you enter the zone click on the a failed initiate who is laying on the ground near the entrance, to receive an enchanted throwing hammer. Find the enchanted throwing hammer in your inventory and drag it to your hotbar.
From a distance, target each of the a terracotta warriors and click on the icon for the enchanted hammer in your hotbar, to incapacitate them.
Proceed with caution as you move through the zone. Though the terracotta warriors are stationary, it is possible to come around a corner or from stairs and run into one before you can incapacitate them with the enchanted throwing hammer. If this happens you revive at the start of the zone and have to walk through again.
If you're 100 with Kunark Ascending gear, the terracotta warriors can't really hurt you, and in fact will die if you have any kind of reactive buff up - and you can one-shot them with your lowest DPS ability. This can be almost as bad as them killing you, however, because it reduces the number you have left to collect. Kill a few, and you'll be searching a while for your last update(s). Kill more than a few and you may have to reset the zone and come back later.
Once they have been incapacitated, their names will turn white and they won't attack you. Click on them to get updates for the quest.
Go back to the exit and return to the Supply Division building in the Village of Shin.
Once you have returned to the Supply Division in the Village of Shin, click on the Supply Cupboard at ( -94, 3, 107 ) /waypoint -93.95, 2.63, 107.15 (to the left of the desk where you got the quest) to turn in your quest and choose your reward.
Time Saving Tips:
There are more terracotta warriors in the zone than you'll need, but you only have to collect 45 to finish this quest. Leave when you reach that number.
The zone is rather maze-like, but the way you move through it cuts down the time it takes to collect all of the terracotta warriors. Because the stairs lead you through the zone in an almost linear fashion, the recommended technique is as follows:
If you move around using the stairs as much as possible (rather than jumping down onto lower levels), you should find each monk quite quickly. When you reach the large middle chamber at ( 1, -45, 22 ) /waypoint 1.21, -44.74, 22.3, you will see two rock paths that slope slightly upwards; one leads to the left and the other to the right. Clear one area (using the stairs movement strategy) first, then go back to the central chamber and take the other path. Doing so makes the quest quite quick.
If you to drop down into the water at the bottom level of the zone, you should be close to the zone exit. This is the fastest way out, unless you want to use your Call to Home or Call to the Guild Hall ability and zone back to the Isle of Mara. If you fall in the water in an pool that looks like it has no way to get out, swim through the underwater tunnel at ( 20, -113, 34 ) /waypoint 20.35, -112.98, 33.82.