Being the Master of the Law of Control, he can naturally do many things that no one else could do, and this is one of them.
He could even erase the alchemy technique from her mind, but doing so is considered mind control and is punishable by nature, so it's not worth it.
So, he simply blocked that part of the mind to prevent her from being able to use that technique. It was risky, so Tang Yin spent the whole night doing that.
It was difficult, but it paid off.
Still, she wouldn't be able to do alchemy until she cultivated an alchemical technique again.
Still, it was enough for now.
After more than 12 hours of spending resources to replenish her lost vitality and to block that alchemical technique, Tang Yin finished and heaved a long sigh the next morning.
