Not a bad critter, but I have a problem with natural creatures which specialize in human prey.
A human population providing enough food for a bunch of squirrels to evolve eating them is not very likely - the group would either move away or attempt to exterminate the squirrels. Either would not provide a very stable diet. A magical creation or unique mutation I could believe. Go to Comment
Not bad but needs work. How does it attack? From the statement "each with a varying set of scrolls it has absorbed and can use" I assume it casts the spells on the scrolls that it is made of, but generally scrolls are one-shot items, so as it casts spells, it is going to weaken itself.
As others have said - flesh it out, and I think the votes will go up. Go to Comment
The hollow horn thing, while cool, really takes me out of the reality of the submission. A horn hollow enough to produce the tuba sound would be large and thin-walled, and not the best for use as a weapon. Perhaps if it were positioned as a magical creature it would work better.