Rats

I think it's multi-layered.

The first is the literal interpretation: it's about the plague.

The second, it's about organized religion and/or political regimes controlling the masses and, on the face of it at least, being used as a political tool for destroying others (Christian religion colonizing the world; the rise in Islamic terrorism; Isreal vs Palestine; the Ottoman, Nazi, Fascist, Khmer regimes and dictators etc). The "Into your sanctum...never to forgive" verse might be a nod to terrorist atrocities caused by refugees of war, but could equally refer to atrocities caused by home grown radicalists of the far right, or perhaps clandestinely supported by the governments.

The third (for which I have to don my tinfoil hat) is about government surveillance in conjunction with technology and social media. We're living in "times of turmoil" where state sanctioned misinformation is contagiously "spreading disease". Through our smartphones, our computers, apps, social media and emails, we "let them in" to the most private parts of our lives, where they can come "for our souls" by mining our data and keeping tabs on us. They come after us relentlessly and mercilessly, and except for going completely off grid we have no way of escaping from them.

I could be completely off the mark.

(PD: This is a copy-paste from a reddit I replied to, in case anyone came across it and took me for a plajorist, hahaha.)