Trial and error for the most part. First I tried to find sequences of characters that, without modification, already looked like real words. I found one in par

Trial and error for the most part. First I tried to find sequences of characters that, without modification, already looked like real words. I found one in particular that turned out to be the name of the city in which the game takes place ("Budayeen", though it was completely garbled). That was a stroke of luck because that word appeared many times in the text and gave me some clue about the adjacent words, since there are only so many words you could reasonably put around the name of the city. I tried globally replacing the characters in DISKTEXT.TXT but was ending up with a word half as long as I thought it should be (for "Budayeen"). One of the fortunate things that happened though was that it revealed to me, by accident, a couple other words (even though the decryption wasn't correct, it made some previously indistinguishable sequences look more like real words, which I pursued). I think it really clicked that I was dealing with bigram substitution when I had to come up with a theory of how whitespace was so cleverly hidden. Here's the lookup dictionary if anyone is interested: http://pastebin.com/pxJU7q7F http://pastebin.com/pxJU7q7F And here's the script that does the substitution: http://pastebin.com/8eYrGbzQ http://pastebin.com/8eYrGbzQ You know, now that I actually think back to it, the lower 4 bits represent one character and the higher 4 bits represent the other. And there I was thinking in bytes the whole time.