When Quinn had first seen all the different levels of beast crystals on board the Dalki Mothership, the first thought he had in his mind was that he could use them to evolve both Vorden and Raten.
There weren't any tier crystals beyond that of the king tier, so there was no need for them to be used as equipment. Besides, there was something better they could get out of it.
A Demon tier beast as an ally was unheard of. Even Mona, who was part of the big four, could only control a Demi-god tier beast. At the same time, it was beneficial for both of them as well. The whole world was currently in a war. In a war like so, people didn't get to choose if they had to fight or not, they had to fight, and it was best if they had every chance they could at evolving so they could survive.