Changes:
- Naga's fusion formula has been changed to a Cobra Kite and a monster from the Mystic group
Reasoning:
Turns out I set the same breeding formula (Drake x Mermaid) for both Leviathan and Naga without realizing it until now. Since Leviathan was defined first, it was taking precedence, which meant Naga was not actually able to be fused. This fixes that.