Its normal attack is a smack with the standard. Bearer Tornado is a spinning two-hit attack on all in melee range. Bearer Breath is a piercing two-hit attack in a line. Finally, it can use Bearer Heal to heal an ally for 27800 damage.
The Standard Bearer possesses a similar attack set to its L'Opera General counterpart, but is definitely the weaker of the two. It has much lower defense and less HP as well. Most characters should easily be able to defeat it one turn. Since the difference between the EXP it grants in this form and the amount it grants as a L'Opera General, it may be wise to lure it to the darkness in order to get it to morph to this form. If, however, your characters are in the light, it will usually come to them and morph into the L'Opera General.
In the PlayStation 3 version of Eternal Sonata, the amount of EXP granted for defeating a Standard Bearer was reduced by more than half, but its HP was massively decreased. Curiously, in the Xbox 360 version, it has much more HP than its PlayStation 3 counterpart, and gives more EXP than the L'Opera General.