Iceberg is a ability that Ice Dwellers are able to have. This ability allows the Dweller to, essentially, take the form of an iceberg. Their body turns off the heat receptors, so that warm temperatures cannot be felt. However, when this ability is in place, the Dweller is much more susceptible to algid temperatures.
This ability is helpful when the Dweller is within a fire, or something hotter than they can usually control. It must be warned, though, that icebergs do eventually melt, so it is not effective over an extended period of time. Iceberg not only eliminates the sensation of heat; it protects the skin from burning, so, if a Dweller would like to hide in a fire to ambush an enemy, it would be completely possible.