oh, that's x-overd one? there's a little "wheel" to the side that tells you how suspectible monster A is to element B. same'ish in fkg. s/m/l, small, medium, large. so large hurts alot, small much less.
so for the baron guy, the dungeon is white element. so assemble the almost black team and manual it to converse enough mp to 1-hit-turn ko the boss. i usually auto it with regular attack, then manual the boss with best spells i've got.