This and the Vile Peaks 10 AF area were opened up when you fought the Gigantuars in the Archlyte Steppe. The two areas tie together a bit during some side quests, and you can get a decent amount of Fragments by traveling between the two. In the 200 AF area, you can get the Honor of the Blitz Squad side quest by using Moogle Hunt to find an out of phase soldier to the south of the Gate in the Dismal Dunescape area. Speak with him to begin the quest. He will ask you to find the other five members of his squad in both the Vile Peaks 200 AF and 10 AF areas. Each one you find will get you a Fragment.

Accepting the quest alone will get you a Fragment. The next Fragment is the Falcon’s Last Light Fragment, which is located in the Another Man’s Treasure area. Head to the end of the tunnel here and speak to the NPC named Falcon. He will run away, so chase him down. When he stops, speak with him again and you will receive the Fragment. The next Fragment, and the last that you can get for now, is the Thunder’s Last Light Fragment. You can find this one on Corporal Thunder, who will be to the northwest in the Another Man’s Treasure area.

Abandon the quest for now and take up the Falcon’s Compass and Twilight Fragment Beta side quest, which you will receive automatically after speaking with Corporal Thunder. You will have to head back to Falcon to ask him about Twilight Odin, an optional boss who you can face later. A Live Trigger Event will occure, to which you should respond Thunder. He will give you the Falcon’s Compass Fragment, which will allow you to progress in a quest in 10 AF.

For now, this is basically all you can do in this 200 AF area. You will have to head to the 10 AF area to take on Twilight Odin before you can complete the rest of the quests here, so head back to the Historia Crux and proceed to the Vile Peaks  200 AF area.