This is a short concept of how Tal-Rey's tomb dungeon could work if it was added.
The entrance is at the Whispering dunes location. A few peaceful bandit NPCs have a camp there. To be able to start doing the dungeon, you first must do several bandit's quests involving killing the bosses. The dungeon is started by getting 6 bejeweled beetles- a rare drop from mobs and bosses, and a sunstone jewel- a rare drop from bosses. Both can be bought at the shop for 25 and 175 ankhs- a new, special currency. After the doors open, a server message is sent in chat and the gates stay open for 25 seconds and additional 5 seconds as they close.
Once inside, the players will face a series of procedurally generated rooms. At the end of each room, 2-5 progressing doors open with an additional "return room", and the players can choose their doors. Each room resets when players leave it, meaning you have to complete the objective first again.
Some rooms:
Entrance: Only content here is 3-4 doors and the exit. The doors are open by default, and the exit is unlocked by defeating Tal-Rey.
Crypt: Contains 3-6 sarcophaguses that spawn spirits and mummies. The sarcophaguses must be destroyed to progress.
Gallery: Has several alive melee statues that try to attack the players. Once they are destroyed, the players may go on.
Staircase: A large set of staircases guarded by special Dustwurms. The players must get past the Dustwurms to progress.
Hallway: Has several alive ranged statues. Once the statues are destroyed, the players may move on.
Temple: Contains a bunch of occult melee bandits. After they have been killed, the players can go on.
Maze: A bunch of twisting passages guarded by a few enemies. It has no requirements other than getting to the other doors.
Archive: A large room in which the players must find randomly placed levers. After you've flicked one on, a door will open.
Dungeon: Has a few occult ranged bandits and a floor that collapses when stepped on or shot. The players must get past the enemies without falling.
Treasury: Contains a lot of gilded stingtails. After the enemies have been defeated, the players may go.
Armory: Contains a lot of bejeweled deathstings. Once they are dead, the players can go to the next room.
Sacred chamber: Only content in this room is a giant sarcophagus that, when interacted with, will initiate Tal-Rey boss fight. After the players have killed Tal-Rey, a chest will arise that holds rewards and the doors to return will open.
Along with chest rewards, all the enemies may drop equipment, consumables and items. There are also many chests along the way, but are well hidden or well guarded. There isn't a set number of chests or a cooldown. Depending on how well you've explored the dungeon, the more rewards you'll get. However, dying means losing everything.