It is a noted reality that ghost pokemon, as a rule, are not satisfied with death. Eschatology differs from biology in the nutrients required, but ghost types must still absorb life energy to maintain their existence in this realm, just as carnivores must eat meat. Brambleghast are not malicious creatures – some have described them as the kindest of ghost pokemon, although in truth Bramblin hold that title – but they are not ready to depart, and have therefore developed ways to feed their appetites.
Travelers' tales of abandoned desert settlements strewn with Brambleghast, combined with this pokemon's well-attested carnivorous behavior, have inspired legends in which swarms of these pokemon devour entire isolated towns, giving rise to the term "ghost town". The truth is less exciting; abandoned buildings are often the only obstacles in the deserts these pokemon call home, and it is wind patterns and inertia which lead them to congregate in these areas, often long after humans have lost interest. And the leftovers of any settlement – not only food and building materials, but records and memories and graveyards – provide an additional incentive for these scavenger pokemon.
Although this myth is not literally true, trainers should be warned that it has persisted for a reason. Brambleghast are not a threat to entire towns, which likely have a wide variety of pokemon to defend them, some of which even a swarm can not cope with. But isolated travelers and small caravans in the Paldean desert, should they not take sufficient precautions, remain in mortal peril; if they are lucky, their spirits will persist to join the Brambleghast swarm.