You will return to your mind many times after the prologue. Many quests and most important story fragments require you to enter the labyrinth. It is also possible to visit the place on your own, without having to wait for other characters to trigger that. There are two ways:
- You must... die. Death of the main character equals waking up in the labyrinth and speaking with the Specter, a part of the protagonist's mind. In order to return to the labyrinth, simply lose a fight or commit suicide (in some places you can order your character to fall or use a piece of glass to cut your throat). Important! During some sections of the game your character can die permanently - this will end the game. Such places are highlighted in the walkthrough.
- You must find someone who will help you get there. Some NPCs, for example Tranquility in Caravanserai, can lead the protagonist into a trance that will take him into the labyrinth. Drinking one of the dangerous drinks in the Fifth Eye Tavern has similar effect.
As the game progresses, the labyrinth becomes distorted. You should visit it from time to time and check if there are some new interactions available.
As for leaving the labyrinth, usually it is very easy. Simply go to the portal shown above. It will safely transport your character to the real world. Sometimes reaching it might be harder - you must for example win a fight. After using the portal you will be taken near the place where you entered protagonist's mind.