Its normal attack is a jabbing attack on any targets in front of at melee range. Its most powerful Special Attack is Fiery Revolution, in which it whirls for four hits of damage on any target in melee range with a strong knockdown effect. Abyss Stone is a distance attack on a single target with a chance of knockdown. Finally, it might use Dark Below to do damage to a target and place them in Darkness Body status, but this is very rare.
The Ancient Fish is the last of this type of fish opponent in the game and by now the general attack set should be well familiar to the player. While the Fiery Revolution can be quite powerful, this monster is generally a lot less dangerous than its dark counterpart, Strong Glory, having less HP and lower defense. By now, most characters should be able to take one of these out in one full turn. Otherwise, just heal if the party is hit by an un-Guarded Fiery Revolution, but otherwise this monster isn't much trouble at all.