Champion Wererat

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.

Keen Smell. The wererat has advantage on Wisdom (Perception) checks that rely on smell.

Indomitable (2/Day). The wererat rerolls a failed saving throw.

Multiattack (Humanoid or Hybrid Form Only). The wererat makes three attacks, only one of which can be a bite.

Bite (Rat or Hybrid Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 11 (1d4 + 9) piercing damage. If the target is a humanoid, it must succeed on a DC 13 Constitution saving throw or be cursed with wererat lycanthropy.

+1 Greatsword (Humanoid or Hybrid Form Only). Melee Weapon Attack: Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 4) slashing damage, plus 7 (2d6) slashing damage if the wererat has more than half of its total hit points remaining.

+1 Shortbow (Humanoid or Hybrid Form Only). Ranged Weapon Attack: +7 to hit, range 80/320 ft., one target. Hit: 6 (1d6 + 3) piercing damage, plus 7 (2d6) piercing damage if the wererat has more than half of its total hit points remaining.

Second Wind (Recharges after a Short or Long Rest). The wererat regains 20 hit points.