The heists of Sableye can involve treasures of enormous value, but gemstones sealed away in bank vaults or deposit boxes are often not even noticed missing until years after the fact – and Klefki are restricted to the Isle of Armor, pursuant to Galar's strict regulations around invasive species. If there is a pokemon which leads Galarians to lock their doors, it is Impidimp – not that, against this pokemon, doors do all that much good.
Impidimp are often described as goblins, but in personality they are more like trolls, for the negative emotions felt when looking for 'misplaced' items only to realize they are gone forever mean far more to these pokemon than the possessions they steal. Impidimp nests do not always contain everything they take, and much of their haul is discarded on the side of the road or thrown into rivers. Yet although Impidimp feed off of negative emotions, they are not harmed by positive ones. An item tossed away thoughtlessly by a passing Impidimp can be a lifesaving boon to traveling trainers and their pokemon.
Impidimp thefts are often rationalized as a form of charity for the poor, and Impidimp themselves as heroic bandits, but this is more credit than they deserve; they will destroy items for laughs, and happily take items from those with anything to steal. And while potions or pokeballs can be a lifesaver for a new or struggling trainer, precious but financially worthless heirlooms and highly specific or situational held items do not escape Impidimp fingers. Yet Galarians have carried the legend of Impidimp, if not the species themselves, around the world, and many when traveling abroad have left useful items on the road in their honor. Paradoxically, trainers outside of their habitat may in fact have reason to be grateful to these pokemon.