Something to keep in mind when playing these games is who constitutes the story's major players, and for what ends they seek to manipulate reality. If you can keep these characters straight, you're halfway to getting it.

-- 1. LAVOS ---------------------- Although this creatures' motives are largely opaque thanks to the fact that it never actually communicates with anything more intelligible than screams, Lucca determines during the final battle of Chrono Trigger that Lavos' primary goal was to influence the evolution of life on the planet so that it could study and harvest the results for its own benefit. When the world was no longer of use to it, Lavos destroyed the planet's dominant lifeforms to create an environment in which it could safely reproduce. Presumably its children would eventually seek out new life and new civilizations - to boldly go where they could repeat their parent's devastating life cycle. Initially Lavos gives humanity an evolutionary boost to help them prevent the Reptites from becoming too powerful, but the alien beast was hardly mankind's friend, since it remorselessly annihilated the world in 1999.

To me it appears that Lavos' real desire is to feed on the energy of the planet while allowing its spawn to gestate; to prevent the planet's indigenous lifeforms from becoming a threat to its well-being during this time, it hinders the advancement of civilization when that becomes likely. This could explain why it chose to give humanity a boost in prehistory - the Reptites would have developed into a species much more dangerous to Lavos than mankind (and would have reached that point more quickly than mankind as well) had their growth remained unchecked. When the human race finally became powerful enough to pose a threat to Lavos in the time of Magic Kingdom Zeal, Lavos emerged to destroy Zeal and set humanity back to a primitive state of reconstruction. Finally, Lavos demolished human civilization once it had reached the extremely sophisticated point reflected in the ruins of A.D. 2300, leaving artificial intelligence the dominant "lifeform" on the planet. Though the machine civilization was probably more advanced in 2300 than humanity was in 1999, there's no indication that it cared one way or another about Lavos, and the creature may have decided that the robots posed little threat to its well-being.

A case could be made that it was Queen Zeal's greed that caused the destruction of her kingdom in 12,000 B.C., but the sudden shift in her personality from respectable monarch to powerhungry madwoman suggests that she was influenced by an external force. Her corruption may well have been caused by Lavos in order to allow the monster an opportunity to impede humanity's development. Or maybe not - this is largely conjecture on my part, so don't get too bent out of shape here.

-- 2. FATE/LYNX ------------------ Fate is an artifical intelligence constructed in Crono's repaired future - a supercomputer based on the Mother Brain design from Lavos' future but with added failsafes to prevent it becoming the murderous force that it represented in the ruined future of 2300. It was partially designed by Belthasar and Lucca and infused with Robo's personality program in a backup circuit to serve as a watchdog for its actions. Fate was the control system for the city of Chronopolis, a research station designed to study time and observe the nature of the dual-reality schism between the Home and Another worlds.

-- 3. THE PLANET -----------------

-- 4. THE GURUS ------------------

-- 5. MAGUS ----------------------

-- 6. SCHALA ---------------------

-- 7. HARLE ----------------------

-- 8. CRONO ----------------------

-- 9. SERGE ----------------------