Thank you! That animated head idea is actually brilliant! Its eyes could lock onto the party's torch very intensely. I might add that when I make revisions.
Its true that the secret passage is probably too good. Currently the only thing blocking a party from it is the lack of a thief or the knock spell. Maybe I'll make the clay area smaller near the obvious entrance, but then note that there are no footprints there. Since the party knows the enemy is ahead of them they should be suspicious of that.