Mission 32: Vanquish the Heartless threat
An unidentified giant Heartless has surfaced in the Agrabah desert. Find it and eliminate it at once.
Roxas is sent to eliminate an unidentified giant Heartless that has surfaced in the desert, and seems to be the source of Agrabah's mysterious sandstorms.
The dark portal puts you into the Palace area. After a quick scene, you gain control of Roxas. There are lots of Scarlet Tangos and Loudmouths around, so be prepared to fight. There also a few chests and an Ordeal Badge to snag as well. When you're done fighting here, proceed to Agrabah Street. There are more Heartless here, as well as a few more chests. On the highest roof in the southwest corner sits a treasure chest and an Ordeal Blazon, but you won't be able to reach them without High Jump. If this is your first time through, you'll have to come back for them later. Proceed to Agrabah Gates and repeat: destroy the Loudmouths and grab the chests. Also, keep an eye out for the Bulky Vendor in the western ally, near the closed-off entrance to the Cave of Wonders. When you are ready, head out the main gate exit for the Sandswept Ruins.
The new Sandswept Ruins is a very large area. You're going to have to watch carefully for chests and the Unity Badge, as they can be very easy to miss in the vastness. Also, the giant Antlion trying to destroy you does not help either. The battle is a little time consuming, but it will eventually go down. Afterward, return to Agrabah. There will be one more scene at the Palace, and then you can RTC.
Stick to using Thunder, as the element is Antlion's weakness and a basic Thunder spell can cause multiple hits against it. Using a Keyblade that specializes in high magic with Magic Units equipped is helpful and having Antlion stun itself by banging into one of the large ruins can help increase the damage of Thunder. Only attack with the Keyblade if it reaches the point where it uses bombs, but aim accurately to avoid wasting your strikes. If you can defeat it before it uses it's whirlwind, then it will contribute greatly to completing this mission successfully.
This one will be so much harder than the last mission as you have a tight time frame to worry about and Antlion is at a much higher level. Besides making sure Roxas is at a high level, you will need Glide for this mission and for your Keyblade, Darker Than Dark+ or Crown of Guilt++ with Magic Units equipped is highly recommended. The same tactic with Thunder must be used here so bring lots of casts and make sure it is at LV5. Defeating Antlion when it gets itself stunned from its lunge attacks when it uses it the first time is a great necessity, as the main problem with this mission is defeating Antlion and getting back to the RTC point quickly enough to get all 3 Challenge Sigils. Be patient if you have to keep repeating this mission until you can get it right.