the bohrok kal were like toa to the island and they were fighting makuta. to help defeat him they made copies of themselfs and made cahdok and gahdok to control them.  Seeing how powerful all the bohrok he tried to take control of there minds( brainwash them) and makuta sucseeded but could not fully wipe there minds. and they still porved to powerful for him and sealed them away. ( the bohrok kal got sealed away sometime around there to) so after the toa defeated makuta the bohrok woke up and cahdok and gahdox thought to help mati nui they had to distroy everything (sence they were brain washed by makuta but not fully) and then the toa go to defeat them ...................... then finaly the bohrok kal wake up and they try to take the place of the toa by defeating them.

PS so that explains why cahdox and gahdox want to restore mati nui and were the bohrok kal came from

PSS sorry if i did not explain well and for all the spelling mistakes

let me ask one thing is this fact or somthing you made up cause your theory sounds unlikely but states a couple facts but as for them bieng actually good i ask one question why would they try to destroy the bohrok also. cause gregf said that we might get to see one kal defeat a whole swarm and so thats where your theory gets wiped away.

well the bohrok kal will prob distroy bohrok swarms because the bohrok are trying to distroy the island.

maybe (just possibly) the bohrok kal tried to make copies of themselves in the beginning of time(hence the bahrag) but idn't want their clones to be smarter than them(the brainwashing tecnique) but the thing went out of control so much that the bohrok put them in shock/unconscouisness. then the bahrag took control of the swarm, tried to take over mata nui, the toa stopped them and the bohrok kal were awakened by the giant earthquake created after the toa nuva were. once awakened, since they were the toas enemies anyway, they were trying to hunt down the toa. the end. pantpantpantpant.

I hope I explained my theory as clearly as possible.

Here's the way I see it:
I think the Bohrok Kal used to be tired of only being with 6 of each, so they tried to make copies of themselves, one swarm per Kal.
But they did not fully succeed: the Bohrok had elemental powers like their own, but they had no soul: so they created the Bahrag Queens to mass-produce Krana.
The Bahrag, however, got sick and tired of being bossed around, and wanted to controll everything on Mata Nui. They caged the Bohrok Kal, and prepared to rule over the island.
Unfortunately, Makuta came along, and chased the Bahrag underground, where they remained. He then sealed the Bohrok in pods, as a back-up plan.