Isn't that obvious? When you're looking to cause destruction, wouldn't it make sense to summon the Eidolon of Destruction?

[If there's one thing he's learned after all this time, it's that villains tend to go for the obvious.]

Did the other Eidolons ever help the heroes in Crystallis?

[He doesn't like the idea of relying on them for help anymore than Takeshi does, but if they are the strong forces that they're said to be, they might be the only way to defeat their foes.]