This page of the strategy guide contains instructions for how to get the Ragnarok back and complete any remaining side quests that are available (which isn’t many) after you have completed the events at the end of Disc 3 in the Lunatic Pandora. Click on the link below to return to that section of the game:
This is also a completely optional page. None of these side quests need to be completed and, if you have completed the events at the Lunatic Pandora, you can proceed straight to Ultimecia’s Castle at the end of the game. Use the link below:
If you are interested in finding the Ragnarok though and wrapping up any lose ends, continue reading below…
While you are on the chain leading up to Ultimecia’s Castle near Edea’s House, take the middle portal by jumping off the chain to the left. This will cause your party to arrive in an area of Centra.
Pull up the World Map and you will see that the Ragnarok is somewhat close to where you are now (its the flashing red dot). You need to get to the Kashkabald Desert. But how can you get there on foot?
This probably does not need to be repeated, but make sure to have Diablos learn 
Enc-None (which becomes available after it learns Enc-Half) enabled. Equipping this ability to one of your characters will allow you to travel around the World Map without being thrown into random battles while you are exploring.
Make your way to the northwest, away from the portal, and towards the northern most point of Centra. There is a Chocobo Forest up and to the east (on the right side of the screen), at the northern tip of the continent.
You are going to need to get yourself a Chocobo for the next step, and in order to do that, you will need to have completed the Chocobo Forest side quest for this area. Check out the link below if you need help completing this side quest:
Once the Chocobo Forest side quest is done, you can use these forests to just hop on a Chocobo at any time, so do that now. These lovely Chocobos can help you get to the Ragnarok due to their ability to walk through shallow ocean waters.
Hop on a Chocobo and make your way towards Cactuar Island and the Kashkabald Desert area (southeast from here). The Chocobo can walk across shallow water, but just be aware that you are going to need to have it run all the way around the southwestern portion of Centra in order to make it to where the Ragnarok is sitting. Its a very long journey!
For starters, lets make sure you are already caught up on the side quests that you should have completed already. Firstly, make sure that you have upgraded all of your character’s weapons:
Then make sure that you have completed all of the side quests that are available in the Deep Sea Research Center:
Complete the short PuPu side quest and the Obel Lake side quest as well:
UFO & PuPu
Track down the UFO in various areas across the world and provide some Elixirs to PuPu to get its card and complete your Triple Triad card set.
Obel Lake
The rewards aren’t great but there is a trophy you can obtain from completing the Obel Lake side quest.
You can also recover any of your lost cards or win some of the cards you left behind as long as you completed the CC-Group side quest before reaching Disc 4. All of the CC-group members are hanging around the Ragnarok, with each of them having different rules from each of the different areas around the world.
If you followed the instructions under the Queen of Cards side quest page, and you landed her in Trabia / Shumi Village, this process will be much easier. The card player that you want to challenge is the Princess Diamond Twins, specifically the one on the left, and having the Queen in Trabia means that the trade rule will sometimes be ‘Direct’ / ‘All’ / ‘Diff’. Obviously we don’t want Direct, as that’s a wacky rule that will cause problems, but ‘Diff’ and ‘All’ will make winning the cards you need much quicker.
The Princess Diamond Twin on the left will typically include in her hand the lowest ranked rare card that you are missing, and will slowly work her way through all of the cards that you either didn’t pick up or that you used 
Card Mod on at some point in the game.
Consider saving your game between each with to make sure she doesn’t accidentally win and scoop up a bunch of your high level cards.
Consider leveling up your characters and Guardian Forces using the two islands that are full of high level monsters:
For players who are completing the game on Steam or PS4/PS5 and want to obtain all of the related trophies, check out the Trophy section for more information to make sure you got them all (or will get them all when you reach the end of the game):
And that’s pretty much it! Its time to make your way to the final dungeon.
