Reduce Resistance and Terror Immuto cheese

[Jinn]

While no Fatemaster would allow this, rules as written it seems as though you can change the TN of a spell to an arbitrary number by applying the Terror Immuto and the Reduce Resistance Immuto.

For example, let's take a Magia with TN 5 and add the terror immuto (TN +1). It is now TN 6, then we add the reduce resistance immuto, lowering the TN of the horror duel provided by terror by 1 with the benefit of reducing the spells TN by 2. This leaves us with TN 4. Both of these immuto can be applied infinitely and the terror immuto increases the TN by 1 each time while the reduce resistance reduces it by 2 while the effect of the spell remains the same. By doing this you can increase the TN of the spell by 50 with 50x Terror and then reduce it by 100 with 50x Reduce Resistance. This means you can either increase the horror duel provided by the terror immuto to an arbitrarily high TN or you can add another immuto (such as increased duration, range or severe damage) as much as you possibly can (infinite for severe damage) without increasing your TN.

Obviously this isn't intended and no sane person would allow it but I'm wondering if I missed something in the rules or FAQ that invalidates it...

I assumed that the reduce resistance Immuto could only apply to target numbers of the Magia but the FAQ states that it can be applied to any duel that is the result of a spell, which should include immuto right?

[Ampers&nd]

your maths are correct, though the horror duel would be pointless it would negate multiple other penalties to the casting value each time. I think your first point about the fm disallowing it is the likeliest solution.