They don't do a lot of damage but require a bumch of hit points and are super annoying when they leap at you and latch onto your face and you have to toggle the joystick and they keep sending more of then at you, it's a good way to level up but SERIOUSLY annoying.
Be aware that some blob things may be able to consume you whole, expecially if you are in a dungeon and fall down a pit, expect to be slowly and escrutiatingly dissolved in acid. They may also devour your entire town but ridiculously slow you guys can just walk away from it at your own leisure.
See also: The Boston Molasses Disaster of 1919! which somehow killed 21 people.