I didn’t get in on this in the 3e days, but I’m tempted now.
I bought the hardcover back in the day and it was/is one of my favorite products of all time.
I’m a HUGE Monte Cook 2e/3e/malhavoc fan. I have all of his 3.x stuff often in PDF & hardcover.
I was all over his Maloavoc forums back in the day.
So - with that said - Ptolus was designed to be a world according to the RULES of 3rd edition.
Monte specifically said, many times, that the campaign setting & the book were designed to reflect a world where the RULES of 3.x D&D were grounding of the game book - spells, monsters, everything was set to reflect the spirit & reality of the 3.x rules.
So I have to wonder, how do you simply switch that over to 5e or cypher system?
One simple example that is the basis for a huge chunk of Ptolus organizations is the concept of prestige classes - they don’t exist in 5E and yet Ptolus was the source of them for 3e and - to my mind- the only place they were used as intended. There are so many fundamental changes from 3e to 5e that would leave so many parts of Ptolus feeling off. I would never attempt to run a Ptolus campaign with 5E - the fit is just wrong.
I can’t even begin to imagine how to port it to Cypher system & keep anything of the original flavour.
It just seems like a bad idea, and I’m saddened by it.
I want to call it zombie Ptolus edition.