The captain with the strongest ice based zanpakuto (Rukia's is based on cold and not specifically ice, just leave it be) takes on the Ice Devil Slayer mage.
1. It's a standard arena fight with both of them starting out in their base forms.
2. Speed equalized. Toshiro starts out in adult mode with his true bankai activated and Gray starts out with his Ice Devil Slayer form.
Who wins?