Emerald Serenade

The Emerald Serenade is an Emblem Heartless that is found in Kingdom Hearts 358/2 Days.

Strategies
The Emerald Serenade always goes along a specific path, so stay somewhere along its path after studying it. Bring along about five Blizzara/Blizzaga spells and a couple of Fira/Firaga spells. Also, if a partner tags along, change the settings so that they won't do anything to move the Emerald Serenade too quickly by attacking it from behind, or else the strategy will be ruined. First, stay somewhere along the Emerald Serenade's path. Once it comes close, use Blizzara/Blizzaga to try to freeze it. Then use Fira/Firaga to deal major damage. Using Fira/Firaga is also useful even if the Emerald Serenade is not frozen, as it may set the Heartless ablaze, which will slowly deplete its HP for a moderate amount of time. Keep this pattern up until it is defeated.

If you're having trouble with that strategy, an equally effective strategy is to get ahead of the Emerald Serenade and let loose a Thunder once it turns to move towards you. This not only damages it, but also increases the damage dealt by any weapon strikes you can fit in afterwards. If you upgrade Glide to its highest level, it is actually fast enough to overtake the Emerald Serenade, so you actually can follow it while attacking.

Etymology
A serenade is a piece of music appropriate to the evening, characteristically played outside the house of a woman, to woo her.