Creating a SQUARE ENIX account will allow you to access contents and services for various SQUARE ENIX games.

You may increase the security of your SQUARE ENIX account by registering a security token. Registering a security token will allow you to use the Mog Satchel in FINAL FANTASY XI, and a free Aetheryte teleport destination in FINAL FANTASY XIV.

Please see here for details regarding the Mog Satchel.