The most useful monster.

Oh! Very interesting division. Can I ask why specifically for offline play? And which ones are preferable for online play? Just curious...
And the Minotaur is actually a good warrior. I really like sending them to the front lines...

For online play, I don't know. And why these monsters are useful for offline play is indicated in parentheses. Here's an example. For instance, there's a squad of 5 Dark Knights against me. I attack with one Fairy and win :) In OFFLINE mode, this battle is perfectly legitimate. I find a good spot for the Fairy and slowly wear down the enemy, using save-loading to manage morale. You'll agree that this won't work in ONLINE play.