A piece of fantasy

A piece of fantasy

A book idea. Now, its a fantasy novel & is way more ambitious than is ever possible, so I'm gonna try to get some opinions. I'm doing it with my friend. This is simply the bare bones of it.
Here's your wrapped up, summarized history.
In the realm, there were humans, normal people. One day, a being arose, wielding the magic of a god. He became known as the universe mage. The universe mage gave magic to the humans. There was no division of magic, into elements or type. One day, along his life, the universe mage recognized how mortal he was, and wondered about what would happen if he were to die. He began to work on new worlds. He created a second realm of people that represent their elements. Monsters, some would say. This realm was to be left alone by the humans. He then made a hole in between the realms, the Third Realm, where no common being was to be. He fashioned a crystal orb and placed it in the Third Realm. When that was done, he divided magic into the elements: Water, Fire, Air, Earth(who later divide into 2 subnations of Desert and Mountain), Ice, Lightning, Metal, and Wood. He granted the greatest being of each field the grand title of Archmage, along with superb magic. He then went to the Third Realm, and divided himself into the 2 overrulers of the reality: The Celestial Archmage & The Time Archmage. In the instance before, he placed every other scrap of power in the orb. If one can defeat the Celestial & Time Mages, they can claim the orb, and gain the power of the universe mage.
This is done in the year 1000, chosen by the Universe mage for epicness.
TIME PASSES ABOUT 8800 YEARS
The villain of this story is my character, Fossil. Fossil had parents who were utterly evil. Fossil one day discovered a book. The book had no title and no author. As Fossil read it, he grew demonic. The book spread its vile magic through him, until he was a being of pure evil. To cap it off, the book gave to him a spell, called Fossilize, which causes the target to turn to stone and bones, and then animate under his command. The spell seemed to be made for him. However, the limitations of his physique were terrible after a childhood of abuse. And so, he cast aside his body and thrust his soul into a pile of semi magical robes. The robes were animate, and he began to plot. He began to rise the scale of power, and eventually was granted council as an honorary archmage. It was then that he struck. Archmage gatherings are big events causing huge crowds to gather to watch. When all were assembled, he used a Mass Fosillize spell to transform the entire crowd. He began to destroy the human race, wiping across the land, not caring for those in his way. All who fell to him, joined him as fossils. The Light and Dark Archmages, the oldest remaining, join power and fuse their magic. When Light meets Dark, Celestial magic occurs. And when a steady flow of each is not available, the magic tears, and forms a rift to the monster realm. Fossil is sucked through, and is banished away. The light & dark mages then die of exhaustion and magic expense.
TIME PASSES. THE YEAR IS 9999.
Humankind is all but extinct. The races are now sub-human. After a certain # of generations, a subhuman's magic prowess dies.

Over these years, fossil has been ammassing an army of humanoid monsters(think goblins and orcs) turned into fossils. A fossil is a hollow package of stone and bone filled with dark energy. Fossil now has an agenda to become the universe mage and wipe out the remaining humans. Effectively immortal in his robes(which are almost invulnerable), he spends his banishment building a massive cannon. This cannon will be loaded with fossils and his own dark power, which will be aimed at the sun. As the source of Light, such a shot of dark energy will form celestial magic, tear a rift, and siphon him to the Realm again.
Fossil has realized that the only way to reach the Third Realm is to open a rift while inside a rift.

Now the good guy will come into play here, the archmage of lightning AND air. He united the nations, though they don't overly want to be united. The catch we want is that Legion, the archmage, is forced into HELPING Fossil. Legion has a virus that deteriorates the body. His wisps of a body are still fading, and he needs a cure. His hands are now only attached by his own magic. Fossil has told him that if Legion helps him, he'll get a cure for the virus. Fossil of course, plans nothing of the sort. Legion is aware of the intention to betray him, and plans to go with him into the Third Realm, where he'll attack Fossil.

When they get to the third realm in the 10,000th year(chosen by Fossil for epicness), Fossil takes on the Time and Celestial mages. He wins, but not before they grab the universe orb and use its power together. When Fossil wins, he begins to take the powers. While the absorption is happening, Legion attacks. Fossil uses his superpower to almost win, but Legion destroys the universe orb. Me and my friend have differing views on what hapens here.

ME: I think the whole world is erased, and time resets with a clean slate.
MY FRIEND: He doesn't think this.
BOTH: Legion and Fossil are both destroyed by each other's magic.