[He is following the group, but he's both slow and injured. Here he is, already notching a fire arrow and bringing up the rear.

Sebastian looks like he wants to cry, but Bradley can appreciate somebody trying their best, even when they're wildly out of their depth.]

Keep on guard. Be ready to fire at the bastard when it begins to approach. You have range, so you can attack it before it gets close to you.

[Once they've made it to the valve he trains his arrow on the monster.]