Having a strong dream (
The Qualified could use Magic Formulas even in the world without any magic element, and they could also detect other Qualified. Those with Drive were being slowly absorbed into the Boundary, which made them weaker.
In case of losing a desire, their rights, the one turns into the magic element. Es used to back up those who lost their rights and disappeared from the world.
Since Ragna the Bloodedge was not a Qualified, and he was born without a Drive, his capacity for magic element allowed him to remove the qualifications of others by consuming their desires using his Soul Eater, making them forget about their dreams.
After Ragna obtained the true Blue, he recreated the world from the consumed desires, and made them a possibility.