In Sumeru, there's a phenomena called "The Withering," also known as "Marana," also known as "The Black Tide." An area that become infected by Marana become referred to as "Withering Zone," and this infection corrupts the surrounding area. Most of the vegetation will die, but some of it will simply be changed into hostile, magic-possessing entities that have to be dealt with in order to purge the Withering. It also attracts monsters, and the bigger it grows, the more powerful the effects of the Withering Zone becomes, enough so that normal people can't enter them without getting extremely sick or dying.

There's more to it than that, but the important takeaway is that the Marana has the power to make a place completely inhospitable and deadly. That sounds a little like this Darkness, don't you think?