Mission 78: Vanquish the Heartless threat

Mission 78 in Kingdom Hearts 358/2 Days sends Roxas to Neverland to eliminate a giant Heartless.

Regular Mission
Destroy the Ruler of the Sky.

Story summary
Roxas goes to Neverland to eliminate a Heartless and discovers that an old foe has been the one causing the trouble in the world.

Mission walkthrough
After Tinker Bell restores Roxas's ability to fly, collect the badges and blazon hovering over the water's surface in various places. Then fly toward the island where Hook and Smee are busy working to initiate the boss fight.

Challenge Mission
Given that you have to chase the Ruler of the Sky, this mission will take a while, so be patient. In order to nab all 3 Challenge Sigils, you can't attack even once, so bring plenty of Fire Magic (as it is most effective) and Ethers/Elixers to refill them with. Fire works best while chasing it (so you can damage the tail), and Fira/Firaga can be used while it is stationary. As you can't use recovery magic, Elixers are your best bet. The Darker than Dark+ Keyblade works well here, as when equipped with all Magic Panels, it deals the greatest magic damage. Dodge the Ruler's attacks when you can, as since your level is capped at 40, you will take heavy damage if you're not careful.