A Cat's Guide to Travelling Through Portals - Chris Behrsin - Bog

The key to open worlds is inside the belly of a dog ...
Since Max, the dog, swallowed the key to enter every dimension, the worlds are no longer safe.
Firstly, the warlocks themselves will do everything in their power to get hold of that key. That's a problem because they're both awfully powerful and awfully evil.
But they're not the only ones who want the key. A mysterious new contender has entered the realm, and if he or his lackeys get hold of the key every single one of the seven dimensions are doomed.
Which means it's once again down to Ben the Dragoncat, his dragon, and his dragon rider companions to save the day. This time, though, they have a whole load of unicorns to help out, as well as a feline cat goddess from an ancient time, not to mention the oldest and wisest fairy of them all ...