Interesting. So he cleared the quest by Analyzing the tower, and thus get it to stop working (the new goal of the shadow world)? I suppose the panels that show us the tower's inner clockwork being zapped red is Desir analyzing the tower itself.
Does that means he already wins the moment he arrived at the tower? All the fighting between the parties, which culminates into fight between him and Adjest, is purely him trying to nurture her and give her a space for an accelerated growth; He can win anytime during the fight by shutting down the tower, but no, he needs his comrade to experience the entire combat and let them grow.