system
Given the following post, respond as if you're commenting on Reddit:
human
[Bionicle] What *exactly* are the Barraki?

Pre-Creeps from the deep mutation, what where they? There are a lot of species in the Matoran universe, but the six of them weren't part of the Matoran "life cycle." Nor where they Rahi. What are they, and where did they come from? 

For that matter, what are Axonn, Brutaka, Bohtar, Sidorak, Roodaka, and the other "unique-species" characters in Bionicle? Nearly half the Dark Brotherhood comes to mind...
gpt
> There are a lot of species in the Matoran universe, but the six of them weren't part of the Matoran "life cycle." Nor where they Rahi. What are they, and where did they come from?

They were presumably designed by the Great Beings for some specialized function that required their unique abilities rather than those of Matoran. Since each was only required for one or two tasks, there was no need to introduce large numbers of each species and so the result was a large number of unique species with a few members each. The most influential non-Rahi species in the Matoran Universe by far are Matoran/Toa/Turaga, Makuta, Vortixx, and Skakdi.

> Dark Brotherhood

I think you're confusing the Dark Hunters and the Brotherhood of Makuta.