Animel, thanks.

I have been doing most of the reccomended stuff - stocking up on potions y doing missions most of all. Since the event seems to fire up every time, looks like I'll have lots of grinding to do before I can even hope to tackle the trolls again - my stock is building up slowly and mostly with lower-end elixirs and draughts.

I was just very confused by what the previous posters said - that the event fires only once and that I can actually go back to the town to heal and thus, bring in full party to the battle. Seemed like a such a nice idea, too... but obviously, that's not going to work.