He truly didn't go to the Alexander Kingdom and slumbered through the entire war, surrounded by millions of void creatures as Nimo fed on them to hatch.
He joined from the start and helped the Anti-Alliance win the war, but it resulted in grave causalities across both territories.
Without Nimo, there was no void army, without a void army, the Mariana Empire gave it everything instead of surrendering the moment the void army made an appearence.
But still, the war was won.
Though, this was nothing but the start of Felix's downfall.
Felix and the tenants watched as Felix was gravely limited with Roc's bloodline compared to the void bloodline.
As a starter, there was no void domain that was capable of killing everyone and anyone in the games instantly.
Still, he was able to inherit Roc's spatial splitting blades, allowing him to go quite far in his journey.