User blog comment:IamJakuhoRaikoben/Chapter 496: Forward, Review./@comment-4945830-20160801190726/@comment-5303512-20160801192127

I don't think that's how Historia works, it is more of how much of the caster's magic they put in, as we have seen, when Neinhart first cast the magic, he was not tired out nor was he sweating, when he used it to bring back the Spriggan members, he was tired out, so most likely, he can bring back someone of his caliber but has to use only what his magic supply can give, this time, it is divided by three. So Historia God Serena was most likely at only 1/3 of his original power.