Wereboar

. .

The monster makes two attacks, using Javelin or Tusk in any combination. It can replace one attack with a Gore attack.

. . If the target is a Humanoid, it is subjected to the following effect.
Constitution Saving Throw: DC .
Failure: The target is cursed. If the cursed target drops to 0 Hit Points, it instead becomes a Wereboar under the DM's control and has 10 Hit Points.
Success: The target is immune to this monster's curse for 24 hours.

. . If the target is a Medium or smaller creature and the monster moved 20+ feet straight toward it immediately before the hit, the target takes an extra 7 (2d6) damage and has the Prone condition.

The monster shape-shifts into a Medium boar-humanoid hybrid form or a Medium boar, or it returns to its true humanoid form, or it returns to its true form. Its game statistics, other than its size, are the same in each form. Any equipment it is wearing or carrying isn't transformed.