Darkside

Darkside is a boss from Kingdom Hearts. It is a colossal pureblood Heartless that Sora encountered 3/4 times. Instances included in the mysterious Awakening, the Destiny Islands, and in the End of the World. It also has a resemblance to Twilight Thorn which could possibly be its Nobody. Sora also glimpsed a number of Darksides within the Door to Darkness before they were destroyed by King Mickey.

In Kingdom Hearts: Chain of Memories, Riku fights a Darkside similar to how Sora fought him. Zexion creates this Darkside from a copy of Riku similar to how Sora faced Darkside in Dive to the Heart where it was created from Sora's shadow. Darkside's name refers to how he is often shown as a representation of the Darkness within others.

Darkside's theme song is Destati. It has a heart-shaped hole in its stomach. It creates Shadows by creating an orb which it puts in the hole in its stomach. The monster can also fire these orbs from its stomach as offensive weapons. It's also the very first boss that is battled in the series.

Darkside is fought at Twilight Town (during a mission involving Roxas and Xion) in Kingdom Hearts 358/2 Days.

A data version of the Darkside appears in Kingdom Hearts coded, which is battled by Sora.

Kingdom Hearts
''Enormous Heartless that appeared in Destiny Islands with Shadows. It led the Shadows in the battle against Sora when he first received the Keyblade. Although Sora defeated it, the island was swallowed by the darkness.''

Kingdom Hearts: Chain of Memories
The Heartless that attacked Sora's home, Destiny Islands. Sora fought valiantly to protect the islands and his memories there.
 * Sora's Story

''The Heartless Riku attracted when he was seduced by darkness. It destroyed Destiny Islands.'' Zexion called Darkside in order to subdue Riku.
 * Reverse/Rebirth

Kingdom Hearts
Darkside is an easy-medium boss, and you can defeat him very quickly. His weaknesses are his head and hands. His attacks in all three battles of Kingdom Hearts are:
 * Darkside punches the ground, causing a dark pool and mild shockwave to form. This attack gives birth to a small number of Shadows.
 * Darkside scoops up an orb of darkness, which splits into many smaller orbs that rain from the sky.
 * Darkside creates a dark force in the heart-shaped hole in its body, which shoots homing dark missiles. These can be dodged by standing behind the massive Heartless.

This is simply a hack-and-slash battle, with no real strategy needed. Simply attack at every opportunity and avoid Darkside's attacks. If you get low on health, defeat the Shadows he spawns as they drop HP orbs, or Cure. If you can climb Darkside's arm and attack his head, you get tech points for every combo finisher landed.

Trivia

 * The Darkside battle shares many similarities with Twilight Thorn, a gigantic Nobody. Both appear in Roxas and Sora's Awakenings, respectively, and are the first bosses of the game. Their Japanese names, Twilight Zone and Darkside, are both science-fiction horror serials.
 * It is the third largest known Heartless, behind Groundshaker and World of Chaos.
 * In Kingdom Hearts, Darkside had a flap of skin where the heart on his body creases at the top. In Kingdom Hearts Re:Chain of Memories this flap of skin was removed for some reason.
 * The first Darkside battle is the only boss battle in the entire series where Sora doesn't say a word during the battle.

Darkside Schattenborn