It would be funny if the second code unlocked a demon that had a fart attack.

I got stuck on a certain boss i think on world 4. So I had to go looking for solutions and the fastest one was to summon a demon that helped with my boss kill (by exploiting its strengths and weaknesses). But it was EXPENSIVE! Easily costing 3 to 4 times the amount I would pay to summon an equal level demon. As a result I didn't feel like I cheated since you can only summon monsters equal or below your character's level. ATLUS' new idea is just brilliant and so simple. 

For players who are curious:

"Thick red skin" is a regular-level Oni with resistance to all four elemental attacks.

"Soothing ice" is a healer-type Silky you can't summon until level 24 (I think).

"Prophecy of wind" is a Mothman with ridiculously high Magic and Agility, and an all-type wind attack. If you can level this demon to match yours, it crushes anything that has a weakness to wind attacks. Easily the best of the bunch.

"Left hand freeze right hand shock" didn't work for me--one too many characters.

Cool post--I'm really digging this code system. Adds a dash of randomness to what is sometimes a dungeon slog.