Originating on Mars at some point in the distant past, Ice Warriors developed a very highly advanced technological civilization. It didn't last; Mars grew colder and less hospitable to life, and the Ice Warrior civilization fell before it. In time, the Ice Warriors survived only in scattered remnants and hibernating sanctuaries. They eventually arrived at a plan to move to Earth for their survival, in the process destroying humanity to secure it. This was a situation that the Doctor described at the time as being of the "this solar system is not big enough for the both of us" syndrome. However, at some pint in the future, peace was agreed on by Humans and Ice Warriors, as in the future the two species are both members of a galactic federation (thus making Ice Warriors one of the few species to have appeared in DOCTOR WHO as both good guys and villains).
By their very nature and the Martian environment, Ice Ice Warriors are used to arctic temperatures, and any cold sufficient to harm them would kill a human almost outright. They are also used to lower gravity, but I'm not inclined to reflect this in their game stats below (and if someone wants to help me do this, by all means...)