Deus Otiosis made this space-castle (spastle) mash-up, the Dimension Door. Here is his description:
A party of adventurers - a warrior, a sorceress and an engineer - in their star-ship has traveled to the legendary Dimension door hub, from which any one of three kinds of dimension doors in the universe can be accessed. However, it is protected by an ancient black dragon, to make sure no such party would ever succeed. It seems to be a very tidy dragon too, seeing how there are not many bones laying around the platform.
Bruce