This was pretty crazy. I had to learn what a playfair cipher was and how to decode it... but it was fairly straightforward after using wikipedia to learn how to do them :)

Yes the key is physical prowess so begin the 5x5 grid by spelling it out, while omitting any duplicate letters, then finish the grid with the rest of the alphabet.

Anybody got this yet? I am completely lost. I get that it’s a playfair cipher so do we fill in the grid starting with physical prowess? Any tips?

Yes, I went way off in the wrong direction at first. There is a Fajr Cup chess tournament. "play fajr" so, 'play chess'... The last names "Welts" and "Weeks" show up fairly prominently in a chess search online. and, golly!, there's also a chess cipher, which it obviously wasn't, but I spent a fair amount of time looking in that direction. I am buffing my nails a little, though, by noting that I did spot the key right away. That's something, at least!

I felt a momentary annoyance with the typo which turned fair into fajr. I looked it up, though, and it turns out it's a thing! I'm going to look at it some more and see if I can cook up a way to apply it to solving the puzzle...

I figured the typo was intentional but I was way off at first. Don't google "fajr cipher", all the top hits are Al-Qaeda related. I might be on a list now. As someone who is new to ciphers I thought this one was a great challenge!

I think that the "play fair" part of the theorem suggests that the entire puzzle is a playfair cipher. (just got the book and think it's awesome btw)