The Secret Triwizard Challenge

"Protego," you whisper. A shimmery shield surrounds your body. You feel reasonably prepared.
You creep into the clearing and notice the floor is sticky. It's too dark to make much out, but you see the shadow of one of the racers being lifted into the sky by the broom moderators.
Well, THAT can't be good.
You hear a skittering just before something jumps in front of the moon and slams down right next to you. It's huge, it's hairy, and it's got eight giant legs. It's...