Cold Flame

Sunny concentrated on creating the alloy. There was little common sense to what he was doing now, since the qualities of the materials transcended the mundane. The foundation of the alloy was a piece of the mystical ice that had once been the heart of the Transcendent Titan, Winter Beast. The metals were no less storied, sourced from the treasury of the royal clan at great expense.

The flame had come from the soul of Changing Star… another Transcendent Titan. Of course, Sunny was not simply melting the materials by exposing them to the immolating heat of her fire — he had to use a crucible, which seemed to defeat the purpose. 

So, he had created a special crucible first, one that was both capable of withstanding the destructive power of soul flame and able to channel it instead of simply transferring heat. The first attempt at casting the crucible was a Memory, but in the end, Sunny had to employ Cassie's help to create a special runic enchantment.