Editing List of Super Smash Bros. series bosses

In the opening, Galeem is commanding a horde of Master Hands against the various playable fighters. However, he then absorbs the Master Hands, turning into a [[black hole]], and uses them to unleash a devastating attack, which only Kirby manages to escape from. Everyone else is hit with snaking yellow beams of light, which imprison them within the eponymous World of Light, before the beams then continue outwards and cover the planet, turning everyone else into spirits.

Galeem attacks the player during the platforming section of the final battle, moving across the screen with two spinning discs made of his wings. He can be repulsed by attacking his core. After the player defeats all of the mode's previous bosses, the player engages in the final phase, where both entities fight each other and the player simultaneously, with them even attacking each other directly if one becomes incapacitated. In the true ending, both Galeem and Dharkon fall into a large body of water and explode, allowing all of the spirits to go free. Once players beat the true boss fight, they earn Legend spirits of both Galeem and Dharkon. Galeem's spirit has no slots, but it comes with a unique ability called "Bane of Darkness," in which damage towards and received from enemies controlled by darkness gets doubled in Adventure mode.

During his boss fights, Galeem mainly attacks by forming weapons from his wings. He is damaged by attacking his core, which moves around the stage. He may form three, later four, drill-like weapons from his wings and slam them into the ground. He may also create a blue orb of energy and fire it into the center of the stage, where he splits into three or four smaller orbs that home in on the player. Another attack consists of Galeem creating a multitude of lines crisscrossing the screen. Laser beams appear along these lines, damaging the player. Galeem can also create three or four small floating mines that explode in a plus-formation similar to that of an X Bomb. He can split his core into three and shoot a barrage of fireballs at the player. He can also teleport around the stage similarly to Master Hand and Crazy Hand.

When his health is about halfway depleted, Galeem is stunned, his wings disappearing and his core falling onto the ground in the middle of the stage. Following this, Galeem becomes angry, his core glowing more brightly. He is now capable of creating bright blue versions of fighters, which attack the player before exploding after a short time. When he has very little health remaining, Galeem is stunned again.

In the second fight at the end of the game, Galeem has two new attacks. He can now create waves of light on the sides of the screen with a gap between them. The waves have no knockback, but they can deal damage even through shields. He can also create two to four eye-like lights that emit shockwaves across the screen. His blue orb attack now creates more smaller orbs. When Galeem is battled alongside Dharkon, Galeem's wave attack is horizontal and is operated in cooperation with Dharkon's dark waves. Galeem and Dharkon can be harmed by one another's attacks. When Dharkon is stunned, Galeem attacks his counterpart by forming a blade out of his wings and stabbing his eye. Sometimes, both bosses disappear, leaving two puppet fighters each.

When defeated in the final fight, Galeem releases a shockwave of energy that deals significant damage and knockback.