Something about you is terrifying. It may not always be evident, but when it is, nobody is in doubt. Others will look at you and be convinced that even if you do not intend to kill them then and there, you would have no qualms about doing so if you were willing to deal with the inconvenience.

At the beginning of each round you automatically, without any action on your part, have a chance to stun all your opponents. Roll 1d20+Level/2 and everyone defends with Mettle. After the round begins you may spend an action to perform that same attack, the normal restrictions on stunning apply.
Furthermore, you gain a cumulative +1 bonus on all d20 rolls and +1d10 damage for every person who has suffered at least 1 wound point of damage by you in this battle and for every level of critical effects you inflict on a person.