You know, it would be interesting to take what we know of the cycles and pick a completely unknown period - the future, or maybe the First Era - and make a completely original scenario out of them, only using the existing Myth races and the guidelines we know, no characters or events from TFL or SB at all.
Imagine, the dawn of the First Era.
A comet rises in the eastern sky.
A dark force arises in the East, and begins wreaking havoc on the world through treachery and deceit, allying around him a group of evil men who come to be known as the Fallen Lords. Nations and races rally to his promises of power and conquest, only to fall to some fate worse than death, bound into servitude by their dark lord.
Meanwhile, a great leader has appeared in the west, building great cities and uniting kingdoms under his rule in the southern lands, and leading the settlement of the wild and wooded northern lands. The uncivilized enemies of man like the fir'Bolg are stuck at in harsh, unwavering attacks, and man in the west expects a bright future, perhaps someday even rivalling the mighty Trow who rule most of the north.
But then the Dark Lord crosses the cloudspine, killing everything in his path and leaving nothing but flattened, blackened ground, earning him the title of "the Leveller". As if it were an ill omen, the great volcano Tharsis erupts, flooding the passes with melted snow and drowing the tiny towns below them. A resistance effort is mounted against the Dark Lord, lead by the Great Hero himself. He searches out powerful artifacts and the mythical "Dreams of Wyrd" - a quest which is countered by the Dark Lord's own quest, to destroy these artifacts before allowing the Light forces to use them.
Behind his frontal wave of assault, the myriad of rival nations united under the Dark Lord's rule begin fighting again. This is largely ignored by the Dark Lord, but the cowering west, which is slowly being decimated itself, tries to use this to their advantage. But that only slows his advance. Inevitably, seeing their cause as hopeless, the allied Light forces strike at the Leveller himself, sacrificing most of their army to hold his forces at bay while the Hero and a small group of men attack the evil Dark Lord.
As expected their army is decimated, and the Hero himself is killed - but he succeeds in wounding the Leveller enough that the Hero's escort can kill him. His powers destroyed, the enemy forces snap out of their trance, and begin fighting amongst themselves again. Our journal writer survives that battle, of course, being knocked unconcious and left for dead when the victors leave the battlefield.
Afterwards, he writes that, while they have defeated the Dark Lord called the Leveller, new seeds of strife have been strewn throughout the world, and most of civilization lies in ruins. It may take a thousand years to return the world to its former state of relative peace, but at least mankind will survive.
Cool, eh?