Darkside

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

Darkside can spawn Shadows and its 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.

The Darkside will be a boss battle in Kingdom Hearts 358/2 Days.

Nobody Counterpart
Twilight Thorn