[CW] Fall synopsis for most shows:

Legends of Tomorrow - "After the defeat of Eobard Thawne and his equally nefarious Legion of Doom, the Legends face a new threat created by their actions at the end of last season. In revisiting a moment in time that they had already participated in, they have essentially fractured the timeline and created anachronisms

— a scattering of people, animals, and objects all across time! Our team must find a way to return all the anachronisms to their original timelines before the time stream falls apart. But before our Legends can jump back into action,

Rip Hunter (Arthur Darvill) and his newly established Time Bureau call their methods into question. With the Time Bureau effectively the new sheriffs in town, the Legends disband — until Mick Rory (Dominic Purcell) discovers one of them in the middle of his well-deserved vacation in Aruba.

Once reunited, the Legends will challenge the Time Bureau’s authority over the timeline and insist that however messy their methods may be, some problems are beyond the Bureau’s capabilities."

Riverdale - " If Jason Blossom’s murder revealed the slimy underbelly beneath Riverdale’s surface, as we enter Season Two, the shooting of Fred Andrews threatens to plunge the entire town into utter darkness."

The ones for Supergirl, Flash and Arrow are just summaries of the series in general and confirmation that some version of Barry Allen, Mon-El and everyone on Arrow is returning.