Upon returning to Sunleth Waterscape, proceed to the Assembly area and prepare to fight another boss. Before heading here, you should again pause the game and enter the Crystarium. The upcoming boss battle is not incredibly difficult, but you can never be too safe, and you probably have lots of experience lying around from your recent battle with Faeryl. You may also want to equip the Grimoire Hat to one of your party members. It is an item that you should have received from a chest in the Nomad Camp area of the Archlyte Steppe. The Grimoire Hat has two incredibly helpful effects; first of all, it will grant you a “Kill Libra” ability, which will give you access to information on the enemies you’re battling, including strengths and weaknesses. Second is the Improved Potions ability, which doubles the effectiveness of potions when cast by the wearer. Using the Improved Potions ability, you can essentially ignore the need for a Medic in your party, for now. Either way, you will be taking on the Mutantomato, a smaller version of the Royal Ripeness enemy that you faced earlier.
Boss Battle: Mutantomato
The fight with Mutantomato is very similar to the battle with Royal Ripeness, excepting the facts that Mutantomato is weaker and can apply more debuffs to your party. It will use Belch to poison your party, and Pouty Pudding to buff itself. It will also absorb Fire, so do not bother with casting. Instead, like you did with Royal Ripeness, cast Aero, as Mutantomato is weak against Wind. Another effective strategy is to use to Commando’s Launch ability, which will deal heavy damage. This battle should not be too tough. Simply exploit the Mutantomato’s weaknesses, use items to cure poisoning, and stagger it before finishing it off with an all-out assault.
You will receive a Mutantomato Fragment and 3,500 experience points. Continue to the Assembly area and grab the Mysterious Artefact from the inaccessible area in the back using Moogle Throw. Return to the Forest Crossroads area and activate the gate there using the Mysterious Artefact. Once you’re back in the Historia Crux, select The Void Beyond as your next destination.
A cutscene will play upon your arrival in The Void Beyond. You should grab two more items while you’re here, so head to the left and use Moogle Throw to grab the two chests. You will receive the Prediction Gate Seal and the Calm Gate Seal. Examine the crystal throne to hear commentary from whichever character is currently your Party Leader. You’re done here for now, so examine the Spacetime Distortion area to unlock two new areas: Serendipity and Academia. Choose to visit Academia first, and you’re off for uncharted lands yet again.