Discussion of level 1 monsters.

There's a distinction between "most useful" and "most powerful." The table lists the most powerful units. I once tested level 1 archers, comparing their effectiveness. The crossbowmen, who lead the table by a significant margin, can defeat any of the other three archer types with the right tactics. Usefulness, however, depends on how and when you use them, and on the specific situation. For example, fairies can be used to defeat hydras.