War Frenzy is an exclusive skill of the Berserker sub-class of the Warrior class. It is unlocked after Cyclone is increased to level 5, and then enabled when one skill point is used, bringing it's level to 1. The ability decreases the amount of time it takes to charge special attacks for 10 seconds. For each level, it decreases the cooldown time by a certain amount of seconds, and decreases the charge time of special attacks by a certain percentage. Using Cyclone Skill gives you Instant 100 Mana, so War Frenzy seems to be a bit bugged.