This reminds me of an anime comic I read once called "Parasyte" where aliens infect humans and take over their bodies and they split open in weird ways and teeth line the split or they form blades or weapons from the body (like transforming the body into whatever is most convenient). They eat other people. It was really bizarre and gory...but very interesting. Now the books are out of print and ghastly expensive. :\

Aaaaah put the mask back on! :D