If you recall, it's revealed that Sorean has gone to Prison Island to open up the prisoned Giant Zanza and improve the defences even further. So your team has to go through a straight forward path. That includes teleporting through the black small area. If you also recall the visions you have earlier, it will play out exactly what you saw before when Shulk tries to take down Metal Face the second time after escaping Ether Mine via Freight Elevator.
There's hardly any explanation but a number of things occurs overtime: Sorean gets killed, Metal Face attacks Dunban, Melia hugs her father one last time and Shulk's Monado is now able to attack Mechons with faces. So attack level 42 Metal Face with all you got and don't forget to enchant your teams weapons if you're controlling Shulk in this moment.
After the fight, just when Shulk is about to give a final blow, Silver-Faced Mechon steps in and it is revealed that Fiora is alive! But the voice is different at the moment. Don't be fooled by this! The different voice will be revealed as a shock later on who is controlling Fiora. So Metal Face and the Silver-Faced Mechon leaves for Galahad Fortress.
Back at the Audience chamber in Alcamoth, Kallian decides to rally the Homs and Nopons in attacking Sword Valley and Shulk with his team will go to Sword Valley via Makna Forest. When you reach Makna Forest in a very different location, always check for quests as it's better than having a disadvantage against tougher monsters.