I'm still looking on the cipher but I think the first part is intentionally misleading. The answer to life, the universe, and everything is 42 or 37, however the quote on the image is a direct statement that "The universe is the answer to everything" which is somewhat different and suggest the universe has something to do with the answer/plaintext.
I'm also doubt that battlegrounds is right, that seems to work off that N or whatever key is used is static, and is thats true you get
b-a-t-t-l-e-g-r-o-u-n-d-s-13-t-14-11-t-13-e-g-14-l-r
Which I cant see any solution for given the used/known letters.
I've tried many online translators and ciphers and got nothing reasonable, I thought for a minute that the numbers were perhaps some cipher of the passphrase or vis-verse, but I'm just spinning my wheels.