I have a small theory, but it is a bit far-fetched...
The Planet and the Dreamstone are creators of dreams, hope, life, etc. . As for Lavos, he could be a sort of destroyer of dreams (one of his attack is named "Dreamless"), and the Devourer of Time is known to be full of hate and sorrow. So, maybe Lavos could be some "corrupted incarnation" of another planet, kinda like the Dragon God too...
It could be why Dreamstones (Red Rock) and Lavos have some kind of bound, and why Dreamstones and Frozen Flame share some similarities.
This theory is rather far-fetched and hasn't got a big, real, basis in the games though, it more like my personal interpretation.