I have made mention of Dorg Fateburn here traversing worlds, this is rather how he does it. Each world there are hidden 'doors', not intractable or visible in any way shape or form just laying around there. And each door leads to a new realm.

The only way to see and open them, is with the right kind of key, a strange golden crystal from another unknown world that just connects to them through unknown magical means. This is known as the Fluppy realm key. They are native to a world of small dog like creatures the Fluppy dogs. Intelligent and adventurous, many of them use these ores to seek out other worlds and explore. By chance, Dorg found himself one, furthermore his strange 'magic' sense of smell could equally find a door as good as any Fluppy dog. If anything, its second nature.

Here we are with Dorg finding a new door, and is mid way of revealing it as he opens its lock...what new adventure will this little Kobold discover on the other end?

And for those who may make reference before looking this up. "Fluppy dogs' are creations of Disney that, rather did not pan out as well as they had hoped. It seem 'hidden doors and magic keys to other worlds' was done by disney ages before 'Sora' came about heheh.

Fluppy Key © Disney
Dorg Fateburn the Kobold, the craft © myself