Duon

Duon is a boss in the Subspace Emissary of Super Smash Bros. Brawl, where it is located atop the Battleship Halberd Bridge. In the game, it is fought by Fox, Falco, Snake, Lucario, Zelda/Sheik, and Peach.

Six Mr. Game & Watches are launched through the glass of the Halberd's control room and land a few feet away from where Sheik, Peach, and Fox stand. They dissolve into Shadow Bugs and quickly reform into the monstrous Duon, which Fox, Sheik, and Peach prepare to battle. Lucario and Snake jump from the control room's window and land behind the three. Falco lands behind the fighters after ejecting from an Arwing as it flies overhead. All the characters work together to defeat Duon. After being defeated the Duon shrinks, and loses all of the shadow bugs that made it so powerful. A lone Mr. Game and Watch trophy lays in its place. With the black, 2D pilots gone from the wheel, Meta Knight regains control of the Halberd. Duon later appears in The Great Maze, where it appears at the same area, atop the Halberd's bridge.

Its attacks involve spinning rapidly, firing a barrage of missiles, crushing the player by jumping, and shooting lasers in a circular pattern, amongst other attacks.

Trivia

 * The name is most likely based on the word "duo" - meaning "two." This is because Duon has two different bodies attached to each other.
 * The design on Duon's wheels is the Yin-Yang, a symbol that represents balance.
 * Duon is often considered to be the hardest boss to beat in Boss Battles, due to its high damaging, high knockback attacks. This is especially noticeable when the difficulty is set to Intense.