Mission 67: Eliminate the Emerald Serenade

Mission 67 in Kingdom Hearts 358/2 Days is an optional mission that sends Roxas and Xigbar to Wonderland eliminate one of the strangest, yet least dangerous varieties of Heartless.

Regular mission
Destroy the Emerald Serenade.

Story summary
Roxas and Xigbar tackle the Emerald Serenade in Wonderland.

Mission walkthrough
You'll enter at the Rabbit Hole as usual for Wonderland. Proceed through the areas as normal, through the Bizarre Room, Hedge Maze Entrance, and Queen's Castle, taking out Heartless and opening chests along the way. Your goal is the Lotus Forest, the hiding place for your target Heartless.

As before, the Emerald Serenade moves in a set path through the area, moving just fast enough you can't run after it and hit it; plus, as its health goes down, its speed goes up. You'll need to pick a spot to ambush it. The best area in this mission seems to be the eastern end of the center path connecting the east and west sides of the Lotus Garden; its trail forces it to double back momentarily as it moves up to a higher altitude, meaning extra chances to deal damage or extra time to cast spells. The area near the door leading to the Tea Party Garden is also a good ambush spot, as the Serenade doubles back and lowers its altitude, making it easier to hit with Blizzard. Clear out the Heartless around the area where you enter from the Queen's Castle first to make it easier to target the Serenade with attacks and spells. Magic is especially useful for dealing with it, especially Fire, Blizzard, and Aero magic. If you wish, you can keep Xigbar active to deal extra damage; his ranged weapons and occasional magic make him especially good at chipping away at the Emerald Serenade's health levels. However, if you wish to use Blizzard spells, you'll want to turn him off, since he will hit the frozen Serenade before you can strike it with another spell or your own attack.

Once you bring down the Emerald Serenade, snag any remaining treasures before heading back to the Rabbit Hole to RTC.