Needs review
Source: Draconomicon

Description: You can overcome an innate vulnerability through sheer willpower.

Prerequisites: Iron Will, Suppress Weakness, Vulnerability to Energy

You can completely suppress your vulnerability to a type of energy. When subjected to an attack based on that type of energy, you take no extra damage.

Normal

A creature vulnerable to a type of energy takes half again as much (+50%) damage as normal from that energy type, regardless of whether a saving throw is allowed, or if the save is a success or failure.