Wererats are cunning lycanthropes typically with sly personalities. In their humanoid and hybrid forms, wererats prefer light weapons and use ambush tactics rather than fighting as a pack. Although a wererat can deliver a nasty bite in its rat form, it favors that form for stealthy infiltration and escape rather than combat.

A wererat clan operates much like a thieves’ guild, with wererats transmitting their curse only to creatures they want to induct into the clan. Wererat clans are found throughout urban civilization, often dwelling in cellars and catacombs. These creatures are common in the sewers beneath major cities, viewing those subterranean areas as their hunting grounds. Rats and giant rats are commonly found living among wererats.

A character who becomes a wererat lycanthrope gains the following features: 

Keen Smell. You have advantage on Wisdom (Perception) checks that rely on smell. 

Damage Immunity. You have immunity to bludgeoning, piercing, and slashing damage from nonmagical attacks that aren’t silvered.

Nimble Rat. You gain a Dexterity of 15 if your score isn’t already higher. Attack and damage rolls for your bite and claws are based on whichever is higher of the your Strength or Dexterity.

Shapechanger. You can use your action to polymorph into a rat-humanoid hybrid or into a giant rat, or back into your true form, which is humanoid. Your statistics, other than your size, are the same in each form. Any equipment you are wearing or carrying isn’t transformed. You revert to your true form if you die. 

When shifted into Hybrid or Giant Rat form, you gain the following additional features:

• Senses. You gain darkvision to a range of 60 ft.
• Natural weapons. You gain bite and claw attacks. Attack and damage rolls are based on whichever is higher of your Strength or Dexterity. The attacks carry the curse of lycanthropy: a non-lycanthrope humanoid hit by an attack must succeed on a Constitution saving throw or be cursed with wererat lycanthropy.