This is placed in the future of the official Warrior books. I hope you enjoy :)
(and I'd like to thank my best friend for the spark that ignited this)
Many moons ago when the leaders were still apprentices, the rogue cats began getting restless and blaming the Clans for everything. They were led by a ruthless she-cat, who had been wronged by the Clans and thirsted for revenge.
The growing rogue conspiracy reached its height when a large force of rogue cats began attacking the Clans, killing cats who ventured out on their own. Eventually the Clans were forced together by the strength of the countless invaders and fought simply to survive.
Then one day a cat named Aspenlight received a sign from StarClan that she would be the spark to start the flames of war necessary to defeat the rogues. So one night she snuck out of camp and went to willow on the hill where the battles first began, and the first young apprentice lost her life.
She found the rogue leader and battled her. Their wounds where horrendous. Apenlight finally killed the leader however the wounds she caused made her weak and she collapsed in the now mixing bloods, dying. ThunderClan found her like this. It was unknown to others she was pregnant.
Aspenlight kitted that night on the brink of death and allowed herself to die only when she heard her kitten take its first breath of life. The cats took the kitten back to camp but it was very weak. Every cat knew that it would die without milk, which the queens couldn't provide without food for themselves, and the rogues had claimed it for their own. The clan cats were overcome with emotion when they saw the skinny newborn shivering already without its mother in the first few minutes of its life. Aspenlight was the spark that ignited the clans' anger, and the kitten was its flame. That night in the early hours before dawn the clans stormed from their last refuge and swept through the rogues like a wildfire, fighting until the last rogue was either dead, or had fled far into the wilderness beyond the lake. Thus the kit was named Flamekit, and Aspenlight became legend in the history of the Clans.
The rouge army was no more and the Clans were at peace again- or so they thought. Little did they know the army was growing stronger and stronger with each passing moon waiting to exact revenge on the Clans for killing their leader. And now, many moons later, they were almost ready.