Mission 41: Eliminate the Morning Star
Defeat the Morning Star.
Xigbar and Roxas go to tackle another giant Heartless and end up with two in the bargain.
As soon as you arrive, it's time to jump into the fray. Once outside, you'll be greeted by three Li'l Cannons. Eliminate them and grab the chest and proceed through the Coliseum Vestibule straight into The Coliseum where you'll be welcomed by your target: the Morning Star. It has a couple of Li'l Cannons of its own to assist it, whose targeting skills will make this battle tricky. You should focus on defeating the Morning Star since the Li'l Cannons respawn.
After defeating it, the Cannons will continue to respawn for a while, depending on how many you managed to dispose of during the battle. Once they're gone, take a look around. You will find most of the treasures and badges of this Mission in this area. The Ordeal set might be tough to reach without Air Slide, Glide, or a similar ability, but they're not impossible to snag the first time around if you come prepared.
When you return to the outside, you will find that a Zip Slasher has appeared while you were fighting inside the Coliseum. Taking it out isn't too bad; it just has a lot of health. Xigbar will help wear the Zip Slasher's HP down. With the Zip Slasher gone and the mission complete it's time to RTC.
Since you can't use Aero Magic to force Morning Star out of it's spinning attack, carefully use Guard to block its attack to do that instead and use a Keyblade with a high attack power. Alternatively you can use a Limit Break by taking enough damage first to destroy Morning Star quicker. Due to the Li'l Cannons on the field, equipping Extreme Ring is not advised unless if you have Glide to help dodge their attacks.
Again you will need Guard here due to your inability to use Aero Magic. Since Morning Star's movements are predictable, after each time it slams into the ground, attack with a combo then back off to avoid the risk of pressing your luck and accidentally missing. Also do not use a Keyblade that has too many combo attacks either. Raising your critical hit stats and using Limit Breaks can also help. Remember you can only make 1 mistake if you want to get all 3 Challenge Sigils, but the mission shouldn't be too hard to do. Also note that Xigbar's attacks don't count as misses - so while his damage is low, you can theoretically wait for Xigbar to whittle down the boss by himself.