Talk:Nero/@comment-30657860-20170419075705/@comment-26441687-20170529000646

Tamamo's explanation of Heinrich at the end of part 3 has

斬れば斬るほどに、彼の剣は高濃度の聖素にまみれ……

Which makes it seem pretty obvious. What do you think the reason for the sword's change in appearance was? Because of all the holy energy it absorbed obviously. If concentrated holy energy is what causes erosion and it's stated that the Angel Halo was absolutely SOAKED in the stuff after what Heinrich did, then it's a logical conclusion to reach that it's more potent after Heinrich's use than before.

It's also stated in the Q and A that while Lucifina created the sword, it's Heinrich that 'tempered' it into its current state by killing tons of angels. Hell, remember that even Heinrich himself eventually merged with the sword by the end.