The Multiversity Guidebook #1

The Batman of Earth-17 arrives on Earth-42 looking for the Cosmic Grail but finds the Batman of that universe reeling from an attack from the Legion of Sivanas. The Batman of Earth-42 tries to make sense of the situation by examining a comic book a Sivana left behind. Meanwhile, on Earth-51 Kamandi and his companions seek Flower while the New Gods watch and discuss how the revival of Darkseid is connected to the creation of the multiverse. Back on Earth-42, the Batman of Earth-17 sends his counterpart to Earth-17 and he joins with the heroes united against the assault on the multiverse.

Description from Grand Comics Database (CC BY-SA 4.0)