I don't know the fiction in question, and I get the impression that the ability circumvents something that the Starblade can do, but your message doesn't fully tell me what the Starblade can do. In my perspective, the evidence seems to imply that the Starblade can protect against magic specifically, but due Golgoth's ability not being magic and instead being a natural extreme coldness, the Starblade's protection is useless. That isn't because the extreme coldness has potency layers or anything like that, it's simply a non-magical ability and thus something the Starblade doesn't protect against. So, if there is no further context suggesting more, then the ability is just extreme cold.