Robot dinosaurs.  That is all.

Maybe a long-standing rivalry between the not-regressed Vorox and the few remaining Skrall?

Plants happened.

Toa Imrukii has been constructing a whole Bota Magna history, complete with one made up language and a second currently in-the-making. I contributed a tad what with a cold dark land inhabited by evil giants that spawned the Skrall originally in early history, but that's it.

Some pretty cool tribe/civilization ideas, but you may want to rely on yourself for any huge epic trippy event/plot-drive.