After finishing 2 species quests, this new main story quest is unlocked, but there's no message suggesting that it's become available. You can choose to do all the sidequests first, or do 2 and move onto this main quest. Take the quest from the middle of Shine center, which is for Union initiated quests. Which basically means they're main story quests. Go talk to the chief, and a new DigiArea called Limit Valley gets unlocked. A bronze tamer duo Gaoh and Lyla will also get sent to the Limit Valley to investigate about the new DigiArea on their own. This map is fairly linear. Once you enter a dark map, watch out for NiseDrimogemon. they're level 27, and can come in 3 packs too. If you are afraid you'll run out of healing items soon, then don't hesitate to use the GateDisk. Meeting 3, or even 2 NDrimogemon in one battle can seriously hurt your party, and you don't want to get game over just before the end of the quest. Soon after you enter the dark area, you'll come across a MysticEnergy. It looks like the ???? that caused havoc in the CITY, or maybe not. It sure looks like it, but there's no specific script to suggest so. After some dialogue the MysticEnergy summons a Seasarmon. And you go into a boss battle against Seasarmon. Seasarmon is only a little bit stronger than the Ndrimogemon. But it has better moves, such as attacking twice or attacking 3 areas at once. After you defeat the Seasarmon, MysticEnergy summons three SandYanmamons. When you're going "sigh this is gonna be a tough one", Gaoh and LyLa appears to save you. And another backstabber! Mystic Energy turns into a Grimmon and you go into a boss battle against Grimmon. Grimmon is a big monster taking 3 spaces. Not only is it big, it's got quite a lot of HP and attacks frequently. Basically all of its attacks are ranged. When you defeat it though, you get hefty 1200 EXP. Yep three NYanmamons would have been a lot easier, but it would have been much less rewarding at the same time. After you defeat Grimmon, the SandYanmamons are taken care of, and MysticEnergy retreats. Now head back to the CITY and report to the chief. Now go and claim the reward at the center.