The medallions were meant to open that rift where the Majin would invade from, there wasn't any mention of those medallions being supplied by the Majin
@Doomer Forming the medallion was always an option but the vampire lords all thought that the majin lord could just open and maintain the rift and collecting curses would be a risk no worth taking. When the heroes chased away the majin lord 10 years ago, the vampire lords were like,"shit, guess we gotta start working on plan B, forming medallions". That 5 minute fight foiled 10 years of collecting curses.
@Necrokora Some people read manga for the pretty pictures the "this material" is nice to look at and it's nice that the group bother to scan it. Otherwise, if that's not your thing, may I suggest the light/web novel? Not being sarcastic, genuinely recommended it.
@Necrokora: Respect the mangaka a little, will you?
The Artist spent hours to days in order to draw those picture and tell the readers their thought/experience.
Do you also feel cheated that a movie spent 2 hours to build the Plot when all you want to see is just 10 minutes of the final battle?
all those illustrations and not one of them was of the adventurer siblings that were uselessly changed into siblings for the manga. so far it seems like they were pointless once again and changing them from the novel but not increasing their story usefulness was a completely arbitrary decision~
@cor3zone got into a discussion with someone on the earlier chapters about how the change was for the better. I'm just pointing out that so far, like in the novel, the characters are useless, do nothing for the story, and changing them for the manga was a completely arbitrary and pointless change.
@traveling_chef This is a re-telling of the story. Checking MangaUpdates/NovelUpdates, the author and artist are the same. Meaning, the change was a preference after considering the original story. So neither arbitrary nor pointless. If it was, the entire story would be arbitrary and pointless, since it came from the same creators.
Also, the characters were not useless. They served to expose Lock's intent to help groom young adventurers, thus giving better character motivation than "I killed the Big Bad already, so I guess I'll start over ¯\_(ツ)_/¯"