Square Enix released an infographic today showing exactly which 12 Eidolons you will fight in Final Fantasy Explorers. Once you beat them, you will also be able to summon them in battle against future fights as well.
In Final Fantasy Explorers, adventurers can battle the 12 formidable eidolons solo or in a party of up to four players. Once players defeat an eidolon, they are granted the ability to summon them in battle while in Trance Mode, a temporary ability where players can also transform into other legendary characters from the Final Fantasy series. After the main story is completed, players looking for a challenge will have the opportunity to battle aberrant versions of each eidolon which are significantly tougher in battle than their original counterparts and feature a different design.
Final Fantasy Explorers releases January 26th, 2016 on 3DS