A big part of understanding the story of Baldur's Gate 3 is by visiting the Githyanki Creche. Whether you agree with Lae'zel's ideas or not, the location Creche Y'llek and Rosymorn Monastery carry some very interesting scenes.
Visiting the Creche is a great way to proceed with Lae'zel's personal story, but it offers some insight into the artifact and other matters. The Githyanki are the ones who attacked your Nautiloid ship, after all. They have been trying to take down the Mind Flayers and the Absolute this whole time.
Should You Enter The Artifact?
It is possible to miss this opportunity because, in order to do so, you have to give up the artifact. Most people think giving the artifact up to some bloodthirsty, rude people will not end well and therefore they refuse to do so.
If you give the Githyanki captain the artifact, it will automatically come back to you because it is bound to you. No one can take it from you, so you are free to show it to others if you want.
After giving the captain the artifact, she will have you personally take it to the Inquisitor since it is bound to you and you alone. The captain will unlock the magical barrier in her room and allow you to walk to the back of the Creche.
Alternatively, you can kill the captain and then destroy the nearby crystal stone next to the barrier to progress.
Vlaakith only appears if you have killed the Inquisitor. She will order you to enter the artifact and kill your Guardian.
It is important to note that Lae'zel will go against you and even try to kill you if you do not go with the Inquisitor and Vlaakith's orders.
If you visited Ghustil in the Infirmary before this event and allowed her to attempt to cure you or Lae'zel, you will then have the option to make Lae'zel stand down. After reminding Lae'zel that the cure did not work and almost killed her or you, she will follow whatever you say.
You can try to convince Lae'zel without going to the Infirmary first, but the DC to do so will be very high.
You should enter the artifact because even if you do, you still do not have to do what Vlaakith or anyone else says, and you will get to meet your Guardian face-to-face.
If you do not obey Vlaakith, she will kill your entire party, and you must restart. You must at least pretend to go along with the orders.
If you try to walk out of the room without doing as Vlaakith asked, Lae'zel will leave your party and try to kill you.
Should You Obey Vlaakith And Kill Your Guardian?
Your Guardian cannot die. They will surrender to you to test your might. If you stab them with the sword, your Guardian will say "I really thought you wouldn't." They will then disappear and reappear healed.
Your Guardian is seemingly stronger than you can imagine, or perhaps this version of them is not real. Regardless, you cannot kill them, and they will turn from trusting and caring for you to not wanting to talk to you at all. You have lost your Guardian's trust if you do this.
Your Guardian or Dream Visitor is an important part of the entire game and story. The Guardian is the only reason you are alive and not turning into a Mindflayer. Without them, you would be an Absolute cultist or, worse, a Mind Flayer.
In the same vein, your Guardian needs you in order to stay alive as well. Therefore, even if you break their trust, they still need you, and you still need them.
Your relationship will be tarnished, which may come back to haunt you later.
Lae'zel initially wants you to kill the Guardian. You can easily convince her that this situation is not to be trusted, and she will go along with your plan.