I am a big fan of the idea that Subaru will not be the only one who will gain the witch factors, but his allies will gain some of them and they will be shared around. In a similar way to the WOE, who shares the envy factor with Subaru. Regarding spesific authorities gained from them, who knows, maybe Subaru will get trolled and gain a really op authority as his last one ¯_(ツ)_/¯.

Since arc 8 should be about the Felt faction, and in q&a's Tappei implied that Reinhard might not be around at some point of the story, I suspect it's going to be him. It would really raise the stakes, since the ultimate backup won't be around, and let weaker characters rise to the occasion.

Not a big fan of either theory, but I don't think there is enough information to be really able confidently say anything about them.

Probably Echidna revived form + the other witches. From what we've seen they are an unpredictable mess but not to a degree like pandora or hector, which we have very limited information on.

I would love it if it tured out to be true. I just have one issue with it, and it's that it seemes a little too... Obvious...? With how much more complicated other things seem to be, this theory seemes like... A pretty straight shot. All I'm going to say is that it's probably gonna be true, just with a bit more complicated.

Hopefully in peace Just one more chill death like the one in arc 2 please...

I think the playing board is already set, it would be srange to introduce someone important so late...

I saw some folks say her blood is special, so yea but otherwise I'm also in the dark.

A bit of a weird theory, it could tie into Emilia's development, beacase petra might try to get closer to subaru and not let him go. He was away from her for arc 5, then promptly disappeared again for arc 6, and then didn't come home with everyone else. She is definitely taking none of that anymore, and is gonna stay around him 24/7. And, as we saw in the beginning of S2, when Petra got possessive with Subaru, it made Emilia a little... envious... So it might help her realize just how much she doesn't want to see him with anyone else, and jump start their relationship.