My amo talked about this when i was smaller and told us kids that in the ''ٱلرُّبْع ٱلْخَالِي'' where he wrote this book some guy said that he saw عبد ال get killed my invisible monsters.
Also ''ٱلرُّبْع ٱلْخَالِي'' (Desert area betwen uae, yemen, oman and saudi) was known by several folks back then to contain unspeakable horrors and monsters that would kill any living human being there.