By acquiring the SQUARE ENIX account, various contents and service can be used. Also, by using the security token for the PlayOnline and the SQUARE ENIX account, account security increases, and "Mog Satchel" can be used in FINAL FANTASY XI.

Please refer to following knowledge base articles for details on "Mog Satchel."
[Q12825] SQUARE ENIX Security Token Bonus Item