Enemies: Dryad lvl 7 x3
Oread lvl 7 x3
This is a simple enough stage that really exists so you have a nice, easy stage to experiment with Søren. Søren is a heavy-duty tank-type character with good defense and very high magic defense, making him an ideal counter to any strong magic-user you come across. His spells are strong, but expensive, so particularly at this early point in the game, you'll want to conserve them for serious threats only.
There's not much to say about the battle itself. Focus your attacks on one dryad at a time, as all six of them can heal themselves, undoing all of your hard work. Also, try to let your weaker characters finish the dryads off for some easy experience.