I think it's Mickey Mouse

Sword Made of Au --> Au means shortcut Gold (Aurum) Mickey's keyblade is golden
I travel the world --> yes, he does
Snekay as a rat --> no one can catch him, it seems nobody is able to
And my cloak will remind you of my enemy --> he wears the same cloak as all Org. 13 members
But dont worry
Ive only come to help --> don't know this one