Baldur's Gate 3 Act 3 Final Battle: All Endings & Best Path Explained

※この記事は2026年06月02日時点の情報を元に執筆されています。
Baldur's Gate 3 does not have a "season" system like typical online games. Developer Larian Studios regularly releases "patches" and "hotfixes," with the latest major update being "Patch 8." This patch introduced cross-platform play, a photo mode, and new subclasses.

After a long adventure, the final confrontation with the Absolute awaits. The countless choices you've made will determine the future of Faerûn and the fate of your companions. The battle against the Netherbrain in the late Act 3 of Baldur's Gate 3, the culmination of its story, is the final stage where you weave the conclusion of your own tale. This article will clarify the complex branching conditions for the endings and thoroughly explain the path to the "best ending," where you save many companions and bring true peace to the world.

Most Critical Branch Point for the Final Ending: Emperor or Orpheus?

Just before the final battle, the biggest choice that shakes the very foundation of the story arises. It's a dilemma: continue to trust the Mind Flayer "Emperor" who has guided you thus far, or free "Orpheus," the imprisoned Githyanki Prince. This choice significantly alters the dynamics of the final battle and the direction of the ending.

The Path with the Emperor

If you choose to continue cooperating with the Emperor, he absorbs (effectively kills) Orpheus's psionic power to counteract the Netherbrain. This choice provokes strong resistance from Lae'zel, a Githyanki companion who worships Orpheus. Unless you succeed a very difficult persuasion check, she will leave the party or become hostile.
Afterward, the Emperor takes the lead in confronting the Netherbrain. You will then have to choose whether to entrust him with the Netherstones to destroy the brain, or outwit the Emperor and become a Mind Flayer yourself, seizing power.

The Path to Free Orpheus

If you have obtained "Orpheus's Hammer" in an Act 3 quest, the option to free Orpheus arises. If you choose this path, the Emperor, whose plans have been thwarted, will betray you and become subservient to the Netherbrain. As a result, the Emperor, a powerful Mind Flayer, will stand as an enemy in the final battle.
On the other hand, a freed Orpheus will be deeply grateful to you and cooperate to defeat the Netherbrain. However, to defeat the Netherbrain, a Mind Flayer capable of fully unleashing Orpheus's power is essential. Here, you face a new choice: whether the protagonist, Karlach (whose Infernal Engine is failing), or Orpheus himself will take on that role.

Choices to Achieve the "Best Ending"

The ending many players consider "best" not only saves the world but also guides the future of companions in the best possible direction. A path that meets the following conditions is considered one such route:

1. Saving the World: Completely destroy the Netherbrain and free people from its mental domination.
2. Karlach's Survival: Save Karlach, who is fated to die from her malfunctioning Infernal Engine.
3. Githyanki Liberation: Keep Orpheus alive to be a force against the tyrannical Queen Vlaakith, bringing freedom to the Githyanki people.

The specific steps to reach this future are as follows:

1. Obtain "Orpheus's Hammer"
First, you must obtain the legendary warhammer "Orpheus's Hammer," which is the key to freeing Orpheus. This can be acquired either by making a deal with the devil Raphael or by infiltrating his abode, the House of Hope, and taking it.

2. Free Orpheus and Persuade Karlach
Free Orpheus just before the final battle. Then, during the choice of who becomes a Mind Flayer, speak with Karlach. Although she has accepted her fate, inform her that if she becomes a Mind Flayer, her Infernal Engine will vanish, allowing her to live on in a new form. She will then resolve to take on this role. This allows Karlach to avoid death, and Orpheus to survive for the greater cause of Githyanki liberation.

• Alternative Karlach Survival Route: If you followed the path in Wyll's personal quest where he becomes the "Blade of Avernus" and saves his father, an option will appear in the ending for Wyll to take Karlach back to Avernus. In this scenario, Karlach can survive without becoming a Mind Flayer, but either Orpheus must be sacrificed or the protagonist must become a Mind Flayer.
• Gale's Special Ending: If Gale is in your party, there's also an option for him to detonate his "Netherese Orb" and self-destruct along with the Netherbrain. This is a way to completely skip the final battle, but Gale dies, resulting in a bittersweet ending close to a bad one.

Netherbrain Final Battle Strategy Guide

The final battle consists of two phases: the top of the High Castle and the Netherbrain's psychic realm.

1. Phase 1: Top of the High Castle
   The goal of this phase is to get your allied Mind Flayer (the Emperor, Orpheus, Karlach, or the protagonist) to the "Crown of Karsus" portal at the back of the map. Controlled Red Dragons, multiple Mind Flayers, and Illithid elites await you. If you betrayed the Emperor, he will also appear as an enemy.
   
   • Strategy Tips: Immediately after combat starts, using "Dimension Door" or "Fly" spells, along with various potions, to move your Mind Flayer quickly to the portal is the most efficient method. The remaining party members should focus on stalling enemies with abilities / spells like "Hold Monster (Mass)" or "Otto's Irresistible Dance," while using summoned Owlbears or Elementals as a frontline. The Red Dragon is powerful, but you can also choose to ignore it and head directly for the portal.
2. Phase 2: Psychic Realm
   After passing through the portal, you'll face the Netherbrain directly in its psychic realm. This phase is a pure damage race. The Netherbrain regularly unleashes powerful psionic attacks and destroys the platforms you're standing on. Always be mindful of movement, and aim for a quick victory using high-damage attack abilities / spells and Action Surge. The character holding the Netherstones will be required to make a saving throw each turn to resist mental attacks, so it's advisable for a character who can maintain concentration to handle this.

Choices Affecting the Fate of Key Companions

The final ending cinematic changes subtly depending on how you concluded the personal quests of your key companions.

• Astarion: If you complete the ritual in his personal quest to make him an "Ascendant Vampire," he will be able to walk in the sun, but his personality will become more ruthless and dominating. If you stop the ritual, he regains his true self, but after the battle, he will flee into the shadows to escape the sunlight.
• Shadowheart: Her ending branches significantly depending on whether you guide her as a follower of Shar or save her parents and allow her to embrace a new life under Selûne's light. In the latter case, a peaceful and happy future is depicted.
• Gale: His fate is determined by whether he keeps his promise to Mystra, the goddess of magic, and gives her the "Crown of Karsus," or if he claims its immense power for himself and aims to become a new deity.
• Dark Urge (Origin Character): If playing as this Origin Character, a dedicated evil ending is available where you embrace the will of Bhaal, the God of Murder, dominate the Netherbrain, and plunge the world into terror in Bhaal's name.

Summary

The endings of Baldur's Gate 3 are not merely a result of choices in the final battle, but a culmination of the bonds and decisions forged with companions throughout your journey. Will you destroy the Netherbrain and become a hero, or dominate it and become a new oppressor? Will you sacrifice your companions, or sacrifice yourself to save others? The "best ending" presented in this article is merely one example. Please make choices based on your own sense of justice and conviction, and complete your unique story. The fate of Faerûn rests in your hands.