Some interesting gaps about Golbez's history

[SilversLyu]

There is also another thing to consider. The 13th is flooded with darkness, which could result in a stronger version of Zodiarks essence even though it's just a part of Zodiark. Maybe irrelevant but food for thought.
Golbez is a walking wild card, the devs could pull all sorts of stuff with him in the last patch(es). I wonder if they resolve some questions you have with the Ascians?

The suspicion about his past is there. They went back to the King and probably got ambushed or betrayed by the King.

[Cleretic]

The suspicion about his past is there. They went back to the King and probably got ambushed or betrayed by the King.

I think the fact that I can say with 100% certainty that this definitely happened is why I'm not nearly as interested in his pre-Flood story. This is definitely the tragic parallel to the Castle Baron sequence, and I've kinda got all the data points that allow me to figure out what happened there.

I know way less about what the hell led to his current situation with the moon--and you're probably right, a Zodiark shard on the Thirteenth was probably beefier than average, if he did indeed beat that then it was no small feat. Not to mention him definitely beating the Watcher, who doesn't seem like someone I'd be comfortable picking a fight with anyway.