Dharkon

Dharkon is one of the two main antagonists of Super Smash Bros. Ultimate's World of Light Mode, and is the dark counterpart to Galeem. Dharkon's body consists of many dark purple spiky tentacles formed into a jumbled mass with a single light-blue eyeball in the center.

Dharkon first appears after Galeem's first defeat, emerging from a large crack in the sky, along with an army of Crazy Hands. It proceeds to power through Galeem's Master Hand army and takes control of the remaining fighters, creating its own world of darkness. After its first defeat, Dharkon flees to the final world along with Galeem, who wages a war against Dharkon and its Crazy Hand army with its army of Master Hands. In the final world, if only Galeem is defeated, Dharkon enchains Galeem and covers the world in darkness. Mario is seen collapsing, apparently dead, as the screen goes black, before Dharkon's eye appears. In the other bad ending, where only Dharkon is defeated, the world is completely engulfed in light, and Dharkon's body disintegrates. In the true ending, both Galeem and Dharkon are defeated.

During the final battle between both Galeem and Dharkon, Dharkon will attempt to damage players with its tentacles while climbing a vertically scrolling stage. It also spawns more dark versions of the fighters, which players must defeat to progress. Galeem also does this in the second half, except with light versions of fighters.

Similar to how Galeem's name is a corruption of the word "gleam", Dharkon's name is a corruption of the word "darken".

Dharkon also appears as a legend spirit alongside Galeem, which both can be obtained by getting the good ending in World of Light. It is tied with Galeem by having the most overall power of spirits in the game. Though the spirit has no slots, it has a unique ability called "Bane of Light" in which fighters take and deal a doubled amount of damage against fighters controlled by light in Adventure mode.

Dharkon makes an additional appearance in Hero's reveal trailer, where it is shown to have created puppet fighters of Marth and Meta Knight.

Battle
Dharkon uses several attacks during its fights, including creating two large darkness waves that move erratically on the left and ride sides of the screen, which players must dodge. Dharkon may also disappear for a moment and reappear as a single tentacle that moves around the stage as well as create two portals and quickly move between both of them, attempting to damage the player. It also may spawn several bombs that will explode, which have an effect similar to the X Bomb item. It can also spawn dark versions of the fighters, who will fight along with Dharkon, who causes large beams to shoot onto the stage, attempting to damage the player.

Dharkon may also attempt to stab the player with its tendrils, exposing its eye after the last hit. It can also fire a barrage of small energy balls from the top left corner of the screen. It is capable of teleporting around the stage in a similar manner to Master and Crazy Hand. The only part of Dharkon's body that players can damage is its eyeball, which may temporarily be stunned and fall on the stage, allowing players to get a few easy hits. After its health is about halfway depleted, Dharkon will become angry, its eye turning red, and will begin attacking faster.

During the true final battle, if Galeem is stunned, Dharkon will form a mallet out of its tendrils and smash its counterpart's core. When defeated in this fight, Dharkon unleashes a powerful explosion that deals massive damage to the player and Galeem.