He is right, Battle for throne sounds too simple, its not even Battle for the throne, which would be the right way to emphasis your current state, but that doesn't really suit too as you have already lost the battle for the throne.
It needs to be something that suggests your throne and kingdom is taken away from you, and you are trying to get it back.
My suggestions according to the plot, haven't played it yet so it's just superficial name:
Revenge of the Fallen Crown
Lord of the Lost throne
Crownless Vengeance
Regent in Exile
Revenge of the Lost Lord