A monodeistic society of devotees to Vermin, the Festering Queen.
Their primary goal is to spread disease wherever they roam, bringing Vermin's wishes to reality.
They are quite similar to The Ravens in their methods of worship and structure, despite Vermin being the ideological opposite of Luna.
Just like The Ravens, they hold familiars, but their familiars vary in species as they've been seen using Rats, Pigeons, and even swarms of cockroaches during operation.
Background
Despite Vermin, the Festering Queen existing since the dawn of time, the Vermin Order only started around the same time as The Raven Order.
Before the first plague, Vermin worshippers used to be disorganized, lacking vision and order, and not posing much of a threat outside of small villages and duchys.
This all changed when Arthur the Rotten started preaching Vermin's scriptures wherever he went, spreading her ideology and converting people to his cause, and as he gathered followers, Vermin took an interest in him.
Appearing to him in a swarm of cockroaches, Vermin told Arthur that he was her champion, The White Rider, The harbinger of the apocalypse, Pestilence.
Gathering his acolytes, he founded the Vermin Order with the sole mission to spread her disease all over the land and wipe out the true disease, humanity.
The First Plague
Arthur, with the powers and knowledge granted to him by Vermin, brought back an ancient disease from the depths of the Earth, a disease that would bring ruin to all known life.
Giving each of his 9 top-ranked acolytes a vial of this pure destruction, he sent them to various places on Earth, so they could start their own branches of the Order, and train new impressionable rotbloods in the art of Pestilence.
And then, he set his plan in motion, causing a massive cascade of death and suffering throughout all known civilization.
Despite the plan being fool-proof, they didn't account for the rise of the New Gods, individuals that ascended to godhood to fill the gap created by the advancement of civilization.