I created the virtues from scratch, but through a long process of research, during which I read innumerable religious texts, philosophy tomes, books on ethics, and much more. Eventually realizing no existing source would work for me, so I spent months organizing and relating virtues and vices into what became the core 3 principles of Truth, Love and Courage, from which I could rationalize not just the 8 virtues of Ultima, but most every other motivating virtue or vice.
I am proud of it. While it is “fiction”… it is also well imagined.
Did you come up with the virtues by yourself or are they based on something from the real world?