Ice Realm (つらら てんち Tsurara Tenchi) is a Caster Type Lost Magic, granting the caster complete dominion regarding the element of Ice within a certain territory. With this magic, the caster is granted access to not only standard Ice Magic but also the ability to freeze anything within the caster's vicinity at command. The speed at which anything is frozen at is almost instantaneous, to the extent that Saxon Xadrez was caught in the magic's effects without being able to defend himself.
Lost Magic in general is regarded almost globally as one of the brands of magic that is closest to the "Source of Magic". In an aspect, it would also make sense then that the more common caster type magics would have branched off of either the Source of Magic or of Lost Magics. In several areas of Earthland, it is thoroughly believed that Ice Realm is in fact the true origin of Ice Magic, although the reliability of the statement is largely debatable.
The magic Ice Realm operates via the caster having a territory, a spherical area surrounding the caster whose size relies upon the capacity of magical power that the caster possesses i.e. The more magical power the caster has, the larger the territory. Within the territory, the caster can freely manipulate any substance, living, inorganic, even magical substances. The manipulation extends primarily to the concept of the substance turning into ice, although several variables also exist.
Relating the magic's ability of near instant manipulation, the caster can easily freeze their targets alive, block their spells or even convert it to ice entirely. Furthermore, the caster can use Ice Magic to a larger, much deadlier effect. The combination of all this renders the caster near invincible in their territory.