"How about two treasures instead of one? Be a little bit more cooperative, please! The Eternal Darkness was already granted a treasure without even participating in solving any trials!!"
Dilan was trying to use the Eternal Darkness to leverage his gains.
It was a fact that the Eternal Darkness was granted a treasure from the City of Trials without doing anything at all. Dilan didn't really care about that, but if it could be used to his advantage, he would definitely not waste the opportunity!
"I want the Soul Weapon; Oricalm, and my Ring of Infinite Element's Constitution has to be upgraded. I want you to add the True Destruction Trait to my constitution!" Dilan requested without much hesitation. The latter was the most important because he was in dire need of the True Destruction Trait.
He could survive without the True Destruction trait but it would make lots of things far more difficult than truly necessary.