One of the many great things about this game is that it offers multiple endings for your characters and companions, depending on the choices you make along your journey. One such question that players have is whether or not to let Gale reform the crown in BG3. Before we go any further, there are some spoilers for Acts 2, 3, and Gale’s fate in Baldur’s Gate 3. So if you’re still playing or don’t want to be spoiled, I suggest you come back later. But if you’re still here, here’s what happens to him.
Depending on whether you're playing as Origin Gale or Companion Gale, the answer to this question will change. But assuming he's your companion and you're looking for an extra cutscene, you shouldn't have him reform the crown.
During the events of Act 2, Gale learns about the Crown of Karsus after you encounter the Elder Brain. After you obtain The Annals of Karsus, Gale suggests that you have him look at the book to learn more about the crown of the Elder Brain and whether or not Karsus actually created it. During these dialogues, you are given various options to encourage or discourage him from reforming the crown. Note that these choices will come into play after you defeat the Elder Brain in Act 3.
If you encouraged Gale earlier, he will leave to reforge it and promise to meet you again after he ascends. If you romanced him, he will also propose to let you ascend after his ascent.