Not very many creatures know of it.
Even fewer live to tell of it.
The humans who entered our world knew of only two lands, Server and File Island. None knew of our island. Digimon spoke of it in stories, but only as a legend, none truly believing it. It was known as the Legend of the Shadow Island.
Yes, there is a Shadow Island, far out in the middle of the ocean. Only the marine Digimon and the winged Digimon can reach it. Only a few of the outsiders escape it alive. It is a small island, home to the Digimon that were barred from every other land. The dark Digimon, the black Digimon, we are called. We are feared and hated, yet it wasn't always so.
Myotismon and the Dark Masters turned the other Digimon against us. Yes, some among us did go over to the dark side, but there were those of us who stayed true to the light. The other Digimon didn't care about this, though. They saw all of us as the servants of the Dark Lords. We were hunted, persecuted, forced to flee.
Shadow Island has been our home for as long as most of the dark Digimon here can remember. However, the elders remember the story of how our lives here came to be.
A tip: It sounds better when you read it aloud in a voice like that little old woman's from Poltergeist. Hehe...