Outside Time and Space. The Interdimensional Gnome, #1

The burglar gnome said, the box was a valuable item, but he couldn't tell Gnom why. Gnom bought it. His friend the tech wiz determined, it was of unknown origin. But it was probably a steering unit, for instance for heat and electricity. Buf pitied people left cold in the dark, somewhere. Gnom set out in the multiverse to search, bringing the elf belonging to the witch in a string around his neck.
The elf could sense unknown impulses, and led Gnom to the world with the dark cupola. It was enormous, made of concrete due to the dragons, and home to thousands of people. With the help of local gnomes and teenagers, the unit was re-installed, and the cupola lit up. Gnom followed one of the burglar gnomes to the burglar gnome world. In this world, every rich person was crazy about the strange, unusable items the burglar gnomes brought back from other worlds.
People sold their things and houses, to get for instance a flat computer screen in a world without electricity. Because of the good prices on the markets at home, more and more gnomes transferred to other worlds to steal other peoples' things. But how to stop them?Buf and Gnom are arrested by the knights, but avoid the wrath of the Gräfin when Hydral and a few hundred other teenagers get them out of there.
Tafn asks the French witch for advice, and the witch takes them beyond time and space to find out if it's possible to cordon the burglar gnome world from the rest of the multiverse.