The Three Devil Girls , often casually referred to as Testarossa and the others , are the three of the Primordial Daemons that, following the resurrection and subsequent subordination of Vert and Bleu to Rouge after their defeat at his hands, agreed to never fight each other directly, instead preferring to outsmart each other in things like games and who could incarnate in the material world first.

Following the Three Devil Girls pledging allegiance to Demon Lord Rimuru Tempest, the group became a sub-group of both the Black Numbers and Twelve Guardian Lords.

They each hold an important job in Tempest. Testarossa is ambassador to the Western Nations. Carrera is the country's judge, while Ultima is its prosecutor. Beyond that they are free to intervene if someone misbehaves; arresting them until trial.