The Poets Palace is the home of The Djinn Master, where he keeps his most prized possessions. It is no longer required for you to complete The Caretaker's access quest to enter the palace. However, you will still need to complete each of the mirror quests to access the higher floors.
Each floor of the palace requires completing an access quest to get to the next floor. Make sure every member of the party clicks on the mirror before starting the quests, otherwise you'll either have to do everything over again, or (worse case) leave and return after the lockout timer expires. The quests are shareable.
Once you've completed the quest, you do not have to repeat it when you revisit the dungeon, as long as everyone in the party has completed the quest. One player cannot "pull" other players through the mirror. Each member of the party needs to have completed each of the quests individually.
The First Mirror quest gives you access to the second floor by killing the animated books found in the area near the mirror. You must slay groups of "an enchanted novel" continuously on both sides of the scriptorium until a marble table appears next to the divider between the areas. Clicking on this table will complete the quest.
The Second Mirror quest gives you access to the third floor by killing Aysor's Eye. Carry the cyclops statues, found on the table in the main room, to the pedestals in the nearby room. If you are alone, you will need to drop the statues to open the doors into the other room, and then pick them back up. In a group, have someone else open the door for the people carrying the statues. Each statue must be placed on a specific pedestal. Refer to the quest article for specific details on how to complete it. After all of the statues are placed, Aysor the Mighty and Aysor's Eye will spawn. Killing them will complete the quest.
On the third floor, there are three rooms which have scarabs in them (emerald, ruby and sapphire). Killing the scarabs will start a ring event which will eventually spawn cobras. After all three of the scarab rooms are clear, you can will be able to gain access to the mirror room in the center and start the The Third Mirror quest by right-clicking on the mirror and select "Gaze into the mirror". It will take some time to gain access to the mirror and complete the quest because the doors on this floor randomly open and close. Once you have completed this quest, you will have access to the fourth and final floor.
On the standard servers, it is possible to complete this instance at level 60 with a mercenary. However, the access quest for the third floor will take some time because you will need to move the statues and open the doors. Having at least one other player with you to open the doors and assist with placing the statues can be helpful.