Something are destined to happened, but when someone outside of it stir things up it caused an unexpected strings of events.
The Hero and Demon Lord are forced to reborn ever so often, and continue to battle for eternity.
... What? Messing with the Demon Lord's Rebirth? That sounds interesting! How exactly? One must wondered how doing so will changes the destined path...
Two soul combined into one. Shunned and changes. Transported without tension.