After we escape the abyss, head to the Dock on The Durandal and enter The Elsa. Save your game. Now that we have DECODER 02 we can open up SEGMENT ADDRESS NO. 2 behind the object against the wall in the left cabin. Open it to find SECRET KEY 22 (Level 3 Class H Skill COMBO BOOST). Demand that Captain Matthews fly us to Old Miltia THIS INSTANT. If you feel like being a SUPER bitch, demand that Captain Matthews turn back around and go to the destination of your choice once you arrive on Old Miltia. The main reason to do this (and it's a good reason) is that as soon as you land on Old Miltia, a plethora of GS Missions become available. Here's all the new Missions you can do, Heffe: