Uncontrollable Rage

You have no ability to control your rage.
Prerequisite: Rage ability.
Effect: You cannot enter a rage voluntarily. If during the previous round something dealt you damage, grappled or immobilized you, or you failed a saving throw against a spell, you may enter a rage; if you do not wish to enter a rage after such an event, you must succeed at a DC 15 Will save or enter the rage involuntarily. You cannot enter a rage more times per day than you are normally entitled to.
Suggested Class/Race: Barbarians
Source: Dragon Magazine #325 (Class Acts - Flaws For Barbarians)