Jorlem: You don't need to reverse-engineer the grief seeds. You just need to reverse-engineer the grief seed interface. Get a grief seed and a magical girl in the same place at the same time with a sufficiency of sensing gear/abilities and have them do their thing. Figure out what the grief seed is doing that lets the magical girl dump corruption into it. Work it from there.
Also - I doubt this has been answered in the show, and it's probably not pertinent to this *particular* fic, but there's an interesting question about the magical economy to be asked. Suppose you're a magical girl who's just defeated a witch and crammed her grief seed full of corruption. Would it be possible to run a profit by letting th seed respawn and killing the witch again without letting the witch negatively affect any of the random nearby people in the meantime? (...assuming you had a sufficiently isolated area)
Also - I doubt this has been answered in the show, and it's probably not pertinent to this *particular* fic, but there's an interesting question about the magical economy to be asked. Suppose you're a magical girl who's just defeated a witch and crammed her grief seed full of corruption. Would it be possible to run a profit by letting th seed respawn and killing the witch again without letting the witch negatively affect any of the random nearby people in the meantime? (...assuming you had a sufficiently isolated area)