Jägerbräu, or Jägerdraught, is a secret recipe of the Heterodynes, dating back to the time of Vlad Heterodyne the Blasphemous, responsible for the creation of Jägermonsters. This potion, distilled from the waters of The Dyne, was given to only the most loyal and strong soldiers, changing them, altering their appearance, and making them nearly immortal and almost indestructible, making them the perfect shock troops and companions of the Heterodynes of old. When it didn't just horribly kill them, of course.