When you enter your rage, your body becomes infused with fire.
Prerequisite: Ability to rage.
Benefit: As long as you are under the effects of a rage, you gain the fire subtype. You gain immunity to fire, but have vulnerability to cold, which means you take +50% damage from cold, regardless of whether a saving throw is allowed, or if the save is a success or failure.
Source: Sandstorm, page 49.