restricting users to rows they created
I would do it like this:
 - Create a table users, where you store your users.
 - Create a table champions, where you store the champions and also in a column champions.users_id the id for that user who created this champion.
 - If a user wants to edit a champion, you check if he belongs to him by checking if champions.users_id is the same as the users ID.

And by the way, no one should be able to connect to your DB. You can define, that you can only grant access to the DB, if the IP is right. For example only localhost or whatever. Your queries should all run through one mysql user.

This are my thoughts about this topic. Maybe possible that there are better ways. But i would go on like this.