Regarding supernatural powers and the descent of gods, Fourth Prince Arthur was clueless. However, by pondering and deducing based on the clues he had, he gradually noticed something was amiss.
Dead rats upon touch, drastic changes in the King's Capital...
All the signs were pointing towards the Church, now in decline.
"Priest, you should be clear that even if I didn't come to you today, Bishop Fole would've told me a lot," Arthur said, "Allying with the Church of the Three Goddesses of Fate could make me invincible, but at the same time, it would cut off my hope for revenge."
"So..."
"I have chosen the Church of Truth."
This was as candid a statement as it could get. To convince Marvin of his sincerity, Fourth Prince Arthur revealed his utmost sincerity. Not only did he disclose the existence of the Knights of the Round Table, but he also expressed his ambition.
Such an ambition, if known to the other three Crown Princes in the King's Capital...
The outcome was predictable.
