Immunity to Fire

A creature with fire immunity never takes fire damage. Even when subject to spells or abilities that reduce a monster's fire resistance, they will continue to remain immune to fire damage.

List of monster types that are immune to fire damage

 * Fire Elementals
 * Fire Mephits
 * Fire Giants

PnP Comparison

 * In DDO, creatures with Immunity to Fire don't necessarily have vulnerability (+50%) to cold. Most do, some do not, and some are exceptionally vulnerable (+100%) to cold.