The "Black Rain" is a mysterious, malevolent force that is inspired by numerous folk tales of unusual rain / weather phenomena - adding a horrific twist with body horror elements.
It is the centre of a creepypasta of the same name.
the origins of the Black Rain are a mystery, it may be extra-dimensional or extra-terrerstial in nature or it may simply be a frightening force of nature mankind has not been able to explain.. given its horrific nature it may also be of demonic origin but no official origin has been given to the phenomena.
the Black Rain has a number of disturbing supernatural qualities such as inducing paranoia, aggression and other negative emotions in victims - it also causes an outbreak of thick, tar-like substance and is said to emit an extremely unpleasant smell.
- the effects of the Black Rain on living creatures is similar (and possinly inspired by) the Purity virus from the X-Files.