There's a possibility someone is purposefully using high-level magic to invade the college grounds with beetles, to get past the magic barrier. It's odd, though, that our past venture underground and this one has lead us to the water supply - the past venture had a witch who tried to raise the water levels, and the current fight used the rain to force the beetles out in our direction. What's more, the beetles seem focused on attacking the students, purposefully.
We piece together the hideout's location.