You can lash out at foes that have been tripped or disarmed, adding insult to injury.

<php>echo “<b>Prerequisites:</b>”;</php> Weapon Mastery (Flails)
<php>echo “<b>Benefit:</b>”;</php> Whenever a foe within your threatened range is successfully tripped or disarmed, you may immediately make a melee attack with a flail weapon against that foe.