Barbarian Rage is an ability available to barbarians. It can send the barbarian into a berserker state, giving bonuses to Strength and Constitution by +4 but a -2 Armor Class penalty. During this, they are also immune to:
Once the effect duration ends, the Barbarian loses all additional hit points gained due to the additional Constitution, which might kill them.
The description of Enrage in-game and in the user's manual is imprecise, refer to the effects used above.