The PCs are all going to be effectively retarded due to their

Dragons

Do you have your system uploaded somewhere? Sounds tantalizing?

Anyways, maybe for low level encounters, the PCs run into a lone wolf type nomadic hunter who is cannibalizing their fellow cavemen, and they have to track him down. The challenge comes from the fact that this caveman is not retarded, and is actually a genius when it comes to traps, misdirection, and bait.

For a high-level encounter, maybe they could stumble on a subterranean or island enclave of dinosaurs that survived the extinction, along with giant gorillas.

>>54302277
Isn't this the one where you have to use your XP to buy words to communicate with, and the players when formulating plans have to point and grunt?

Big tigers.
Everywhere.

>>54302277
Oh my god, this sounds phenomenal...

>>54302277
>Og

BBEG

Something that's entirely understandable by us but terrifying without being described in language we'd understand?
Mammoths, for instance. It's just some incomprensibly enormous THING with giant teeth that groans like the living dead and covered in fur that deflects your stone tools. An arm that flexes like it has no bones picks them up and throws them aside with ease.

Saber-toothed tigers, hippos... or even lightning storms and floods could be phrased to be terrifying and unknown foes.

>>54302277
The übermensch of caveman someone that is double the size of the other ogs

>>54302788
On this note, trying to appease a pack of slavering monsters with meat sacrifices to avoid getting eaten could wind up with them getting a surprise puppy.