The Ice Warriors are tall, bipedal reptilian creatures with clamps instead of hands. They are always found clad in thick scaly armor with bulging hips, and a headpiece with red eye-holes that doubles as a space helmet. They are also rather slow, lumbering instead of walking easily, and their breathing is heavy and labored. When they laugh, it comes out as several short hisses. Ice Warriors apparently have a greater fluid content than human beings.
The Ice Warriors come from Mars, but as their planet is dying, they are very motivated by the search for a new planet of residence. To this end, they have attempted to invade Earth several times. They arm themselves with a powerful sonic gun mounted on the wrist, which bursts the brain with noise and affects the central nervous system - it can kill, paralyze, and melt both metal and ice. Eventually they also develop a rod-like weapon with a yellow core which appears to be another variety of sonic weapon - it seems to destroy by warping the tissues of the body and, ironically, can emit levels of heat high enough to melt metal doors. Their spacecraft are also armed with sonic guns, and they use ion reactors, fueled by mercury isotopes, for their engines.
A military hierarchy characterizes Martian society. Groups of Warriors are led by an Ice Lord, who in turn answers to a Grand Marshal. Where the Ice Warriors have scaly armor, the Lords wear smoother armor, with a more streamlined helmet and a sparkly black cape. The Grand Marshal has a sparkling sequinned helmet and sparkly skin.
Accustomed only to the cold Martian temperatures, the Ice Warriors are extremely sensitive to heat. Individual Ice Warriors have greater or lesser sensitivity - some will pass out at temperatures of 40 degrees Centigrade, while others remain somewhat active at 60 degrees Centigrade. But if enough solar heat is directed at them, they will melt away entirely. They can also be killed by other Ice Warrior sonic guns, or stunned with ammonium sulphide. Bullets merely ricochet off their armor.
When the Doctor first encountered the Ice Warriors, one of their spaceships had crashed at the foot of a glacier and been buried in an avalanche. Once brought back to life by intense heat, they tried to destroy a nearby base to get fuel for their ship, but were eventually destroyed by the heat of an ionizer ray. On their next encounter, the Ice Warriors tried to take over a Travelmat station on the moon, with the intention of transmatting fungal seed pods to Earth. The pods expand and explode, releasing their spores which then cause more pods to grow. Soon the ground is covered in a layer of foam and growing spore pods, which gradually lowers the oxygen content of the atmosphere to one-twentieth of normal, killing off the human race and enabling the Ice Warriors to colonize the planet. The Doctor found that the pods were susceptible to water, and was able to destroy the fungus with rain. The Warriors' invasion fleet was then misdirected into the sun.
In later years, the Ice Warriors renounce violence altogether, except in cases of self-defence, and some of them join the Federation security forces. But there still exist breakaway groups who would like nothing better than to go back to the good old days of death or glory.
