The burned carcass of the rat is a charred memory engulfed by the raging fire. Its sudden eruption makes Kell move away, if only to not get burned by it. Then he notices the rock in Wilhelm's hand and it scares him. If the Acolytes can make the sweet kid Wilhelm usually is act like this what else they can force them do?

"But they are! All of this is! The danger, deprivation, the illusions! It's all deception! It all serves the same purpose! Playing with our minds, our senses, perceptions! Everything! To whatever evil end they have planned! How can you be so blind to not see it?!"

That last thing he said. It's stupid. Of course, Wilhelm can't see it. That's the poison they fed him working like intended. He came out from this cursed ritual seeing through some of the deception. Definitely not something the Acolytes wanted. But he also came weakened. More than he's already been. Unable even to find peace in those precious seconds he could escape to Horizon. To even catch a glimpse of a better place. Having to fight with Wilhelm that this is somehow better? It's too much.