The limit break is the special move, it shows up when you're at 10% or less of your HP (the same cutoff level for entering battle so you'll never go in with it on).
I have avenged those who died at the hand's of Troll, but I won't be doing it again any time soon, it'll cost me 600 gp to heal from that and it only pays 150 GP.
Doing a comparison of our stats: (First stats are troll's second are mine)
Troll is significantly stronger than me (300 vs 249)
I have a vastly higher defence (200 vs 405)
I have slightly more HP. (300 vs 319)
I have vastly more mana but that doesn't matter much atm. (1 vs 314)
I'm level 23 and fully equipped and have the fire element but with no enchantments.
Troll is somewhere around Level 20 I guess. Maybe 18 or so if Mana actually did something.