The low number of casualties was the reason why the academy dared to let the special instructor's candidates conduct their assessment at this lake.
Unfortunately, for the beasts and the monsters in this lake, the low number of casualties meant it was getting harder and harder to get good quality 'prey'.
The monthly feast also often didn't yield any good result, unless the visitors dive into the water, which would greatly increase the chance of being hunted down.
Thus, for all the above reasons, the beasts had tacit cooperation and they chose to attack the barrier's part that already had visible cracks on it.
Coincidentally, wasn't that 'chosen' barrier was the one right in front of Ainsley?
And so, the beasts all geared up to launch their various attacks, but Ainsley had already spread her love virus to the several monsters just now when they leapt into the air.