The Dark Island is a location in the world of Ninjago.
The Dark Island, much like its light counterpart, the island of Ninjago, is shaped somewhat reminisce of a dragon, albeit upside-down. It is predominantly black-colored, having little native vegetation or animal life. Little is known about the specific composition of the island, although it is known to contain vast mines of Dark Matter, a substance with the capability to turn anything evil with a mere touch. It is assumed this was a result of the Overlord's inhabitation of the island, as the First Spinjitzu Master likely would not have formed it when he created the world.
The island is apparently able to be controlled by a single switch, as Lord Garmadon demonstrated. In the episode The Stone Army, Garmadon accidentally landed on the island. Happening upon the Overlord, he was instructed to turn four switches implanted within a circular rock. Doing this caused the rest of the Dark Island, an area likely many hundreds of square miles in area, to rise from the sea.
The Dark Island was first formed centuries ago, when the First Spinjitzu Master split Ninjago in two in order to contain the Overlord. When it was split, the Overlord, by an unknown means, was magically forced to stay on his island, while his army was put to sleep and trapped underground. At an unknown time, the island was sunken under the sea.
Years later, Captain Soto and his crew attempted to find the island with their ship. They failed, their ship sunken by a massive storm, due to No Eyed Pete's incredible lack of steering ability. The crew all perished, and the ship floated back to the Ninjago mainland, later to be discovered by Sensei Wu and the Ninja.
Decades later, Lord Garmadon finally came upon the island. Upon raising the island from the sea, via the Overlord's instructions, the Overlord gave Garmadon control of the Stone Army. Soon afterwards, Garmadon began to mine for Dark Matter under the surface of the island. This was in order to get the right materials to build his superweapon.
During this time, the Ninja (Kai, Cole, Zane, Jay, and Lloyd) arrived on the island and searched for the Temple of Light. Upon finding it, the Ninja discovered their Elemental Robes and Elemental Blades, and Lloyd his golden powers. Upon the finishing of the Garmatron, the Ninja challenged Garmadon. During the fight, the Overlord possessed Garmadon's body, broke Lloyd's leg, and created a portal to the mainland of Ninjago. He and the Stone Army disappeared through, leaving the Ninja trapped on the island.
After a short period of time, the Ninja rediscovered the First Spinjitzu Master's golden mech, and used it to fly to Ninjago in order to repeal the threat of the Overlord.
Whether or not the Dark Island has been colonized, returned to the mainland of Ninjago or has merely been left alone in currently unknown.
- Temple of Light