Before entering Shadowfell in Baldurs Gate 3, it is important to complete as many side quests and objectives in the available areas. Shadowfell is a crucial area in Baldurs Gate 3 that contributes to the main storyline, and entering it is a point of no return where you will be making game-changing decisions that lead to important outcomes. Here are some things to do before entering Shadowfell:

• Complete all possible side quests and objectives in the available areas.
• Discover and close out Moonrise Towers.
• Complete the following quests: Avenge Gluts Circle, Find Arabellas Parents, and Find Rolan in the Shadows.
• Save more times than you have to and pay close attention to the game-changing decisions you will be making.

It is also important to note that entering Shadowfell has the potential to modify the Shadow-Cursed Lands entirely, which means that most of the secrets or side quests in Act 2 will become unavailable. Therefore, it is recommended to complete as much as possible before heading into the lair of the Nightsinger.