Well, Ba'al had been hoping that Carl would actually try and eat him, that way he would've been close enough to try something like stabbing the beast in the brain.

The claws are going to make it awkward to get close as well...

So Ba'al suddenly drops, falling to the floor. Well, he slows himself down a bit once he's near the floor, darting forwards at the last moment to make sure he doesn't land right on top of the spores. A blood red shield shimmers into existence on his other arm, and he uses it to keep the spray of worms off him as he runs towards Carl's leg.

And yes, I'm afraid that since this is his own personal shield, it's damn hard to break. The worms that strike the shield knock him about a bit and keep him off balance, slowing him down, but they're not doing much to the shield itself.