What is the point of "A Glaive out of Time"? [Spoilers]

[Ah! So Spider!]

I understand that it's supposed to be a way to interact with your character from Comrades or whatever, which I haven't started, but is that... Literally it? Supposedly the batteries are for Cindy to build something that "Produces a lot of light without using too much power"... But you never even see Cindy post time-skip, and there's nothing new as far as I can tell when you go back to the past.

TL;DR, Is this quest ONLY a neat little thing where you can see your Comrades character if you have one? There's not even an EXP reward so that just seems really silly to me... Surely there was a better way they could've done that without making a totally pointless quest.

[CatPerson]

It's the way to get one of the new bro-specific Talisman accessories (new to Royal/Windows Ed. content on release). IIRC it's Ignis' one.

Each Talisman has a chapt. 14 sidequest in order to acquire it.