Certain warriors can work themselves up into a fighting frenzy, a whirlwind of destruction in which all concern for personal safety is overridden in favour of mindless violence.
To represent their fighting fury and lack of self-preservation instincts, Frenzied troops gain +1 Attack and the Immunity (Psychology) special rule.
A unit that includes one or more Frenzied models can only choose Hold or Stand & Shoot as a charge reaction.
If, during the Charge sub-phase, a unit that includes one or more Frenzied models could declare a charge, then it must do so unless a Leadership test is passed. If the Leadership test is failed, the Frenzied unit must declare a charge against the nearest viable enemy.
A unit that includes one or more Frenzied models that attempts to restrain pursuit if it beats a foe in close combat suffer a Leadership modifier equal to the result they won the combat against that unit by. For example, if the Frenzied unit won the combat by 3 and the enemy unit flees, the Frenzied unit suffers -3 to its Leadership if it attempts to restrain from pursuing.
Unlike other special rules, Frenzy can be lost as the game goes on. Models retain their Frenzy for the entire game unless beaten in combat, at which point the enemy have succeeded in knocking them into a less fanatical state and the Frenzy (together with all associated rules) is lost.