The Nighgate

The Nighgate is the name for the whole island that appeared off the coast of Prosi.  Shortly after its appearance dragons of unknown color started pouring out into the world and thus began the Draconic War.
The war ended with the Battle of Nighgate with a massive ship battle which the fallen ships and soldiers of can still be found off the coast.
No mortal has walked the island since that battle though it is still kept under watch by the metallic dragons.