Dragon Island

Dragon Island was an island located far beyond the waters of The Lone Islands. Dragon Island was inhabited mostly by wild goats, and herds of wild swine, as well as a single dragon. It also has a mystery of how the Lord Octesian died.

History
The Seven lost Lords went there as one of the many islands they visited. One of the lords, Lord Octesian, died on the island, either having turned into a dragon (after finding the Dragon treasure that was on the island) or killed by a dragon.

Later Caspian X and his friends discovered the island, when Caspian was on his voyage to the end of the world. Eustace, upon discovering the Dragon treasure, turned into a dragon. The crew of the Dawn Treader did not know what to do with him, until Aslan un-dragoned Eustace, turning him into a human once again. The crew of the Dawn Treader, once reunited with Eustace, sailed away from Dragon Island. Before they left, Caspian had the following inscription carved into a smooth cliff facing the bay, which they had used as a harbour for the Dawn Treader: -

DRAGON ISLAND

DISCOVERED BY CASPIAN X,

KING OF NARNIA, ETC.

IN THE FOURTH

YEAR OF HIS REIGN.

HERE, AS WE SUPPOSE, THE LORD OCTESIAN

HAD HIS DEATH.

Film Adaption
In the Voyage of the Dawn Treader film, Dragon Island and Deathwater Island were one of the same. Also, the island was a volcanic wasteland, not green with animals, like how it was described in the book.