The Anti-Monitor and Psycho Pirate watched as Pariah saved Lady Quark from her Earth's (6) destruction.
In the 30th century of Earth-1, Barry Allen spent some time with his wife, Iris. When lightning flashed across the sky of their climate controlled world, Barry got into his Flash costume to check it out. He found the anti-matter cloud closing in on his world and began to vibrate back in time to inform the Justice League. When he stopped, he found Mirror Master fighting another Flash.
The heroes there were costumed officers of the law, not vigilantes. Pariah and Lady Quark appeared as Batman, Robin, Wonder Woman, Hawkman, and Hawkgirl (of Earth-D) took down a criminal. Barry talked to the Flash of that world and got him to understand he was not a comics character, but his doppleganger from another earth. He introduced Barry to the Justice Alliance of America.
Pariah was able to get to Earth-1 and bring some of its heroes to Earth-D. The Anti-Monitor was not impressed with the show of force. He sent shadow demons. They attacked. Hawkman and Hawkgirl - brother and sister - of Earth-D were the first to die. Superman (D) was injured, and the heroes retreated - his Fortress of Solitude destroyed. Earth-D's Superman died in the arms of his wife, Supergirl. The two Batmen had a difference of opinion when Earth-1's told the other heroes to "toughen up." Earth-D's heroes returned home to say good-bye to their families (Batman had a wife and three kids - one being Dick - Robin).
The Green Lantern of this Earth's sector, Tagin Sur, swooped down to attack the shadows. His ship was destroyed, and he gave his ring to a pilot named Jose Hernandez before he died.
Robin and Wonder Woman (D) were caught up in the antimatter cloud. The Flashes built a huge cosmic treadmill, hoping they could transmit the citizens of the dying Earth-D to another. The Flash (E1) disappeared and appeared before the Anti-Monitor. The remaining Flash was losing energy. The Earth-1 heroes returned home; the Earth-D heroes continued to fight the losing battle.
Instead of arriving on Earth-1, the heroes arrived on the Monitor's satellite.