If it exists, Stanth has at least some knowledge of it, even if they only know that it exists. If something they know about has aspects that they don't know about, they know about those hidden aspects. The chances of Stanth actually being able to locate that knowledge is probably 1 in 100, for the more obscure and uncommon things. The chances of Stanth actually caring if they don't use it and don't fight it is effectively zero. So most members of Stanth have extensive knowledge of most common forms of magic, and then counters to deadly magics that come up every now and again. Note: If Stanth has no reason to care about something (aside from the purpose of sticking information on it in the archives), they won't.