The concept of polar opposites is a concept as old as the universe. Everything has an opposite which steers things towards balance.
Xior and Becca were the same, one carrying the yearning heart of a Dragon which burned because of grief and the other carrying the broken scale of a Dragon which froze because of losing someone.
While the things they carried were merely objects which burned and froze them, the two were reflected in those objects. Xior was the fire, Becca the ice.
He acted first and spoke later while Becca remained calm and didn't jump headfirst. Both of them symbolized Yin and Yang as much as the objects they held.
Even their ambitions were the opposite and thus they were in harmony and balance with each other.
Each step towards the summit was hard, their speed had lessened due to Becca getting frozen completely after some time but she never stopped.