They look like gigantic worms with sharp, enormous teeth. They are one of Dark Mother's servants.
Unters are very wild and are vicious carnivores. A servant of Dark Mother said that they are untamable because they eat their trainers. Saddles are attached at the back of these creatures so the minions tried to tame them because it is difficult for even Dark Mother's powers to control them. It is said that they are blind and deaf, possibly caused by Dark Mother so they couldn't eat her.
They cannot attack flying adversaries which is why they retreated when the Guardians flew to evade them. Later, some of the minions are able to control the Unters and fight the girls with them although the Guardians beat them this time by stunning them with flight and then attacking them.