Alter Aeon Online Help

Keywords are:  'warrior skill flanking attack'

Skill: flanking attack          Lvl 29 Warr  (21%)
                                (helpful)   Requires: retreat
                                Group: Warrior group tactics

Usage:
flank
flank <opponent>

This high level warrior skill is used to flank an opponent that is busy
with another target.  This is typically used in groups, where a flanking
fighter will rally several other group members and lead them to attack
from an unprotected or less protected angle.

While this tactic can be effective from time to time, it cannot be used
often or it loses its potency.