These small vermin are made from a combination of deep emotions such as fear and desperation, mixed with the unstable emotions of their vessel. When those emotions flare up just right, they are then conceived within their vessel's body and born into the world. They only have one goal in mind and that is to grow into the original form. But because of their premature birth they are fairly weak and require a lot of energy in order to properly grow up. Once it grows to a certain size, it'll evolve into its next stage and begin the final preparations for its rebirth into a full Witch.