How is opposed Thaumaturgy handled? Opposed Evocation is straightforward: treat it as Attack vs. Block, or simply opposed Discipline checks. But Thaumaturgy has fixed target numbers, and no measure of success other than "it didn't blow up in your face."
Example: The villain doesn't want to be scryed, so they cast an anti-scrying spell of complexity X. Can the players cast a scrying spell of complexity X+1 to find them, or can the villain simply not be spied on magically until the players work out some narrative reason why they can pierce the villain's defenses?
Another example: The players have set up wards around their home that prevent the villain from entering. Can the villain simply throw a huge Thaumaturgy spell at the wards to destroy them? If the players are on the ball (but unable to disrupt the spell in person), how should their attempts to bolster the wards or magically disrupt the villain's spell be modeled?