Back To Back

You excel at watching your allies' backs and helping them watch yours. As long as you and an ally are adjacent to each other, neither of you can become Off-Guard due to flanking unless both of you are flanked. If you're adjacent to more than one ally, all eligible allies can benefit at a given time.

The benefit is negated for everyone if at least you and any one eligible ally are flanked, but not if your allies are flanked and you aren't.