Overlord Tornadus is a Flying Type Weather Buffer. Usually placed in Teams with Lugia, Ho-Oh, Rayquaza and others.
Being a buffer, usually any personality with +Speed is good enough.
Overlord Tornadus main goal is to survive, so it's usually better to focus on defensive Hidden Skills.
Disclaimer: This is a basic recommended build. Please keep in mind that some builds might need to be changed in order to adapt your pokémon to the current meta, or to simply adapting yourself to the enemies that you play against.