The Son of the Ancient Sun

Cactus is trying to get into Thunderclan to become a spy for his father But When he finds an injured apprentice and saves her life after a flood, He sees an opportunity to prove himself to his father and take down the clans that wronged him in the past. But when a prophecy comes to the medicine cat and Cactus realizes what his father is truly like he must face the decision: fight with the clans or watch them all burn:

Cactus has been tasked by his father to spy on Thunderclan to help him in his destruction of the clans. But when Cactus finds a near dead apprentice and saves her life he is welcomed with open arms to Thunderclan. But as he finds out clan life is much better than his father's group he starts to have a change of heart. Then his brother's, who have made their own groups to help take down the clans, start attacking them. He must choose between his power hungry father or his incredible new life.

This falls under fair use of the USA constitution and I do not own Warriors or any of the concepts taken straight from that series