Go back and recover the corpses from the previous battle. Give it the corpses to eat to distract it while you run by.
Since attacking it is stupid and useless, tell our resident superhero to attack it. That's what superheroes do, anyways! >:-D They have freaking plot armor!
Go for the joints!
Joseph: John! You take care of that thing! We'll try to find a way to distract it!
John: Isn't that redun- ah nevermind I'm on it.
John: Hey there, drill face!
Steve: So now what!?
Joseph: Now we all run back to the beast nest, gather up all the corpses, and feed them to it. We'll sneak past it while it's distracted!
Teresa: What kind of plan is that!
Joseph: A brilliant one! John how you doing up there?
John: Fine! Ah! Not hurting it very much though!
Jormungandr: ROOOOAAAAAAARRRR
Joseph: Aim for the joints!
John: What joints?!?!?! It's an eel! They don't have joints!
Suddenly the discs on the beast's sides start moving. A terrible earsplitting noise fills the room as the walls and ground start to shake. bricks start falling from the ceiling,and the tunnel you entered from caves in!
Steve: Now what.
Look at that HUGE LOGO on its head, and see if you have seen it before on any, say, representatives of SECRETIVE PARAMILITARY FORCES recently.
(Seriously, what is it with sci-fi conspiracies and their urge to put their logo on all their secret projects?)
Well if you remember correctly, that's the logo of the Xeno Defence and Research Agency, they were formed somewhere between the seconds nd third martian wars. But that doesn't make any sense, they fight beasts, not control them. And they're suppose to protect you.
...right?
((Apologies for the wait. I lost track of time at some point. Here, have some concept art as an apology.))