Keen Smell. The wererat has advantage on Wisdom (Perception) checks that rely on smell.
Shapechanger. The wererat can use its action to polymorph into a rat-humanoid hybrid or into a giant rat, or back into its true form, which is humanoid. Its statistics, other than its size, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.
Multiattack (Humanoid or Hybrid Form Only). The wererat makes two attacks, only one of which can be a bite.
Bite (Rat or Hybrid Form Only). Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 ( 1d4+2 ) piercing damage. If the target is a humanoid, it must succeed on a DC 11 Constitution saving throw or be cursed with wererat lycanthropy.
Shortsword (Humanoid or Hybrid Form Only). Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 ( 1d6+2 ) piercing damage.
Hand Crossbow (Humanoid or Hybrid Form Only). Ranged Weapon Attack: +4 to hit, range 30/120 ft., one target. Hit: 5 ( 1d6+2 ) piercing damage.
Wererats are cunning lycanthropes with sly, avaricious personalities. They are wiry and twitchy in humanoid form, with thin hair and darting eyes. 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. Wererats that are accidentally cursed or break loose from the clan's control are quickly hunted down and killed.
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.