User blog comment:IamJakuhoRaikoben/Chapter 452: The Prelude to the Final Battle, Review./@comment-31.132.65.53-20150914233004/@comment-25111584-20150915074901

We have too little info on the Curse, imo. For all we know, some types of Magic might harm the user unless refined, the Contradictory Curse just being one such harmful effect. If KotSS arc was canon, I'd point to Angel's situation. And most experiments related to resurrection could have such adverse effects. Like radiation poisoning. But superstition termed the research taboo and the Curse the work of a God. Law would also be a similarly harmful Magic.

But we can conduct nuclear experiments comparatively safely today. Similarly, Mavis refined Law into Fairy Law. And R System and Eclipse Gate could also have been made safer in 400 years.

The above is just an example though. For all we know Ankhseram might be a compassionate dunderhead who saved Mavis from dying as a result of Law by cursing her. Same for Zeref, who could have died from the experiments. Or Ankhseram might just have believed that Zeref does not mind any side-effects as long as he can get enough time to perfect a way to revive his brother, so 'blessed' him with immortality. Too little info, as I said.

What I wanna know is how so many people seem to know so much about the Curse even before Zeref was afflicted? Were there similar cases before him? Then what happened to them?