The most useful monster.

Medusa is definitely very useful! It's strange that no one mentioned Medusa and she's not in the ranking. :( Although Minotaur is there. But on the other hand, Minotaur is more useful for offline play because of the "block" which, theoretically, can be turned into invulnerability to physical attacks. And even having just one Minotaur can change the outcome of the battle.