Baldur's Gate 3 forces players to make some extremely difficult choices (such as if you should free the Pixie or not) will little to no context on how those choices could change the course of the entire game. This makes some players leery about making decisions.
One choice you must make is whether or not you should kill the Dream Visitor that is constantly bothering you while you are trying to sleep. This choice has some major effects on how the game plays out in the end.
Updated by Erin Rice on August 17, 2023: This update includes more information on the Dream Visitor as well as how killing him or not can have dire consequences.
Who Is The Dream Visitor?
The Dream Visitor is probably the most enigmatic character in the entire game. It is the character that you create after you create your own character at the beginning of the game, despite not knowing what it is for. While it isn't exactly clear at that point, the Dream Visitor will be an extremely important part of your playthrough. They also go by the name the Guardian and are the ones inside the Astral Prism claiming to be protecting you from the Mind Flayers and the tadpole that they put in your head. It can be extremely difficult to understand what they are and how their role with change the course of the game.
Should You Kill The Dream Visitor?
While completing Lae'zel's personal mission, she will ask you to help her find the Githyanki and ask for their help with the tadpole. During this quest, you will meet Vlaakith, Lae'zel's queen. Vlaakith will tell you to go into the Planecaster and kill the Dream Visitor that is residing in there. If you do this, you will have the option to kill the Dream Visitor; however, this cannot happen. If you go this route, the Dream Visitor will heal themselves and get upset at you for falling for Vlaakith's lies. You will learn that Vlaakith's plan all along was to trick you into killing the Dream Visitor and then was going to attack and kill you and your party at camp. This allows you to realize that the Dream Visitor truly is trying to help you. If you ever succeed in killing them, then you will learn the hard way that they're important.
If you choose to disobey Vlaakith, Lae'zel will leave your party, and you will have to kill her. This option is unavoidable if you decide to disobey Vlaakith. However, if you want to avoid upsetting the Dream Visitor and Lae'zel, you can simply enter the Planecaster and listen to the Dream Visitor before ultimately leaving. If you do this, you will have to fight your way out of the Githyanki group. However, this means that you will keep Lae'zel and make sure that the Dream Visitor doesn't get upset. The only problem with this scenario is that you will be fighting the entire area. There won't be anyone on your side besides your party.