The Last Battle was written by C.S. Lewis and published in 1956.
The Last Battle
Narnia...where lies breed fear...where loyalty is tested...where all hope seems lost. During the last days of Narnia, the land faces its fiercest challenge - not an invader from without but an enemy from within. Lies and treachery have taken root, and only the king and small band of loyal followers can prvent the destruction of all they hold dear in this, the magnificant ending to The Chronicles of Narnia.