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Freeze Gram (術式凍結) is a counter magic. 
Freeze Gram has limitations, that it can only counter before magic invocation, because no magic is able to overwrite invoked magic. Freeze Gram is more efficiently used against any Non-Systematic Magic. Since Cast Jamming is only a psion noise, which is a type of Non-Systematic Magic itself, Freeze Gram is most efficient against Cast Jamming.