Where we at now?
In short:
There's a game which, when solved, gives the following string of letters (plus a "!" at the end):
DLTHQSXERGFWPPBLWCENLRAEKNIIHUDDLPESAFB!
We have to remove/keep some of those letters, but it's not very clear which; at Discord, we are working on it.
Once we have that, we might have to decode/decrypt it using either a numeric key hinted in Freddy's first pic (which could be 20345 or 24345 with or without 97 somewhere) and/or the "+4,-2,+3,-1" from the second pic (like we did with puzzle #11).
It seems that the result will suggest the password to input here:
https://vailrenovations84552723.wordpress.com/the-last-puzzle-before-the-final-puzzle/(Oh: the pic of the band looking at the screen is the coolest thing ever!

Thank you Mike, Jordan, John, John, James and Freddy!)