Forbidden Spell's Side-Effect
Since Count George already lost enough of his face in front of his citizens, he decided not to use the low-ranking forbidden spells as he already used them twice and both didn't work against Yuan.
And despite them being forbidden spells, they couldn't even put a little scratch on Yuan's body, which is a great disappointment for him and also an embarrassment.
And since the two forbidden spells didn't even make a scratch on Yuan's body, despite the spell possessing the destructive power of lightning. Therefore, Count George decided to take a risk and used his most powerful forbidden spell which is a Tier-6 spell, not many people know about this spell except for his wife and his butler, who isn't with him at the moment.