After unleashing the demonic moles on the masses, the Grand Water Immortal finally saw Kai Syaoran as a big problem that had to be dealt with as fast as possible. He was not the only one who noticed this, but since he was the closest, he believed that it was his duty to kill off this menace before the spell that could free demonic beasts spread even further. Immortals were powerful and could do without tamed demonic beasts, but those who had a tamed demonic beast doing their bidding were far more powerful, since in most cases, the beast would be in the same cultivation realm as its master. Since a demonic beast is always more powerful than a human in the same cultivation realm, this would make the immortal far more powerful than if he did not have the beast.
This meant that almost all immortals had one or two demonic beasts at their beck and call. They didn't need the beasts, but the beasts were simply far too useful to be left alone.
