From Raging Swan's website:

In the murk and stink beneath a bustling city’s streets, scheming families of wererats scurry through the fetid sewers, often riding their vicious and bad-tempered cockroach steeds or accompanied by their filthy, disease-ridden dire rat pets.

Using dark magic and manipulative rituals to break and twist the spirits of society’s most vulnerable members, the natural lycanthrope elite convert and conscript afflicted wererats to join their families. Those daring the cloying, fetid darkness of the sewers are fortunate if all they carry from the sewers is a raging fever for far worse fates lurk among the filth and detritus of the city above. Wererats of the Roach-Run Sewers includes:

• Four feats
  
• Five new class features
  
• Five spells
  
• Three magic items
  
• Seven wererats (ranging in CR from 3 - 9); each wererat benefits from three stat blocks, one each for their humanoid, hybrid and animal forms
  
• Four other stat blocks (ranging in CR from 0 - 9)