I had a theory a long time ago that went like this:
remember when the toa shed the exo-suite and the bahrag said "you fools! you have no idea what you have unleashed!"? maybe the kal lived hidden in the protodermus and that's what we saw in the picture with tahu nuva rising! they could detect elemental energy! the exo-suite hindered the elemental energy, so when they got rid of it, the kal could detect them! the tubes opened for the kal to go up, but the toa surprised them and went down! the bahrag must have trapped the kal in there, and then they were exposed to the protodermus (or, maybe they were like that before) and became kal! the bahrag trapped them because the kal could become potential allies with the nuva!
it's a very old theory and needs a lot of patching up:wacko: , and it probably isn't the how the story will go, but don't you think the part about the kal detecting elemental energy could be true?
confusing, isn't it?