Isaac's home planet, Earth, is destroyed. These things happen, shockingly often actually.

Normally, there's no loose souls floating around, needing to end up somewhere. Due to a clerical error, and a chaotic god, Isaac's next life is going to be much different to his first.

Tasked with ruining the easy farming grounds of Gaia, Isaac simply decides to roll with his role for now. He wasn't an emperor in his past life or anything like that, but 

Without anything better to do, why not take over the world in his spare time?