User blog comment:IamJakuhoRaikoben/Chapter 371: Tartarus Arc: Part 2 - Song of the Heavenly Dragon, Review./@comment-70.233.129.87-20140215021447/@comment-173.79.102.70-20140215061650

Cana's using the same card magic as Sho. Sho was able to handily trap Erza in one of his cards, as well as a whole casino full of people. So a far more powerful Cana being able to get all of Fairy Tail into cards is no stretch.

We saw the sword end up against their cell last chapter. It would need to be some type of magic sword for them to get through their bonds with it. It showing up is rather convenient, but that's about it.

Kyouka's curse kind of let her inflict immense amounts of pain on Erza, without inflicting much in the way of real damage. If Erza, as a kid, after being tortured by guys that couldn't do that, and who either blinded, or ripped out one of Erza's eyes, could go on to lead a slave revolt almost immediately after being freed, she can stomp a single weak demon.