Ririn

Ririn is a Modified Soul built by Kisuke Urahara, one of three created alongside Kurōdo and Noba to test Ichigo Kurosaki and his friends before the Bount arc. She appears as a small blonde girl in a bird-shaped cape, and her default setting is contempt for everyone in the room.

Her ability is illusion. Ririn can wrap an area in a false environment or make a target see something that is not there, which is why the test she runs on Ichigo's group works as well as it does. Combined with Kurōdo's shapeshifting and Noba's teleportation, the three of them cover most of what a support unit needs, which was the point of building them.

Being a Mod-Soul in a gigai means she cannot be killed as long as the pill itself is intact, and she survives assaults from Hollows, Bounts, Shinigami and Arrancar across two anime-only arcs without ever softening. She spends most of that time insulting Kon, who is the only other artificial soul around and therefore the only person who can be insulted properly. She is anime-only, and the arcs she carries are the ones the series uses to give its side characters something to do.