My creature has the natural ability to cause thunderstorms and heavy rain simply by coming into contact with the Earth’s atmosphere, its body producing several chemical compounds and unstable molecular disruptions in the air that they spark off large thunderstorms, that grow the longer it spends time at the surface. It is also believed that should Kyogre wish, it can use these unstable forces to create and manipulate a number of electrical-based attacks, creating its own storms to blast opponents with thunderous bolts and lightning. What is my creature skin made of that allows it to create unstable disruptions in air and what compounds are released that allows them to create large thunderstorms and heavy rain?
Magic/suspension of belief
There's a lot happening in (thunder) storms. It is an incredible amount of water. And incredible amount of wind. An incredible amount of static electricity. To generate these, you need to:
- Assemble an incredible amount of water, mostly vapour.
- Move incredible amounts of winds, in the creatures case irrespective of the air pressure.
A storm has a tremendous amount of power. The lightning is one of the lesser amount of energy, akin to some normal powerplants up to modern nuclear powerplants.
To achieve a storm yourself you'll likely need more energy than several nuclear power plants can generate, assuming a good efficiency. If all that energy comes from the skin of a creature it is very strange to attack this way. With so much power it can probably use it more easily and efficiently in a more direct way.
Chemicals just won't cut it, nor nuclear or technological means.
There really isn't any way a creature can make more than a strong wind blast in a tiny area. Let alone getting tons of water into the atmosphere. You need magic, technology indistinguishable from magic or just suspension of belief.