Adult PC Game: Greiya: Seven Kingdoms - Chapter 0.1 by The Historian Archive

Overview:​
The Third Prince of Jivanna, having earned the disfavour of King Jivanne - likely due to being born the son of a mistress - is sent on an ill-supplied, undermanned, and underfunded military campaign, that by all laws of common sense ought to end with failure, and possibly death.​

Accompanied by an odd group of mismatched councilors and military commanders, though each is undoubtedly talented, none are without their flaws.
The most unusual of the bunch, his advisor - Elizabeth el Nobilia, the First Princess of Nobilia - claims herself to be a "goddess of victory", but more than anything, seems to be a devil taken human flesh.

Survival, let alone the coveted throne, seem far out of reach. The Prince pushes forward nonetheless, with his "theory of coexistence", his pride as a giant warrior, his beliefs, the fate of his sister, and his very life on the line, he fights.