Passwords are used for summoning demons, either from others or from these special passwords. For instance, Soothing Ice will give you a Level 23 Silky with Bufula, Glacial Blast (random Heavy Ice), Diarama, Media, and Shooting Spree. You can also output passwords from demons in your compendium, so it's basically a Pokemon-esque trading, but without the use of cables or anything like that. Most passwords are just assortments of random numbers/letters/symbols though, rather than phrases like the ones in the Atlus e-mail.
Atlus actually has a Strange Journey password forum for people to post theirs.
Edit: I just tried each of those passwords. They're not bad for starting players, as 2 of them are below level 10, one is around 12, and the last is of course level 23. They're pretty good demons for their level though.
Also, for anyone on the last dungeon, I ran into the second technical boss fight
and holy crap is it brutal.
Atlus actually has a Strange Journey password forum for people to post theirs.
Edit: I just tried each of those passwords. They're not bad for starting players, as 2 of them are below level 10, one is around 12, and the last is of course level 23. They're pretty good demons for their level though.
Also, for anyone on the last dungeon, I ran into the second technical boss fight
Jiminez