Stalas is not, technically, exhausted.
He hasn't slept in... it has to have been several weeks at least. Hasn't eaten in somewhat longer than that. There's a crackling prickling pain under his skin sometimes, when he goes too long between lyrium deposits, but he feels neither hunger nor thirst.
He's pretty sure he isn't literally going in circles, but he's long past the areas depicted on Gorim's smuggled map. So much for escaping to the surface. For sheer lack of anything better to do he's been trying to search out Branka's old expedition, but he hasn't seen anything to indicate he might have stumbled onto their trail. He's probably going to die down here. No, he's definitely going to die down here, and be eaten by darkspawn. He hopes they all die of lyrium overdose.
A giant spider dashes out of a side tunnel. He meets it with drawn daggers. It has three friends. He kills those too. Now he has spider fluids all over him, which may actually be an improvement on darkspawn blood. He sighs and turns away from the dead spiders and continues on his way.