Amalgam Comics was a publishing imprint shared by DC Comics and Marvel Comics, in which the two comic book publishers merged their characters into new ones (e.g., DC Comics' Batman and Marvel Comics' Wolverine became the Amalgam character Dark Claw). These characters first appeared in a series of twelve comic books which were published in 1996, between the third and fourth issues of the Marvel vs. DC miniseries. A second set of twelve comic books followed one year later.
The two comic universes came together when the two physical incarnations of their respective universes (referred to as "the Brothers") became aware of each other after eons of slumber. To prevent the Brothers from destroying each other, characters from each universe battled to determine which universe would survive (a real world vote by readers of the series was conducted to determine the outcome of five of the in-comic matchups, with three of them favoring the Marvel hero). Access, a character created for the event and co-owned by Marvel and DC, served as a gate keeper who became stuck while traveling between the two universes.
When the fighting concluded, neither universe was willing to go. To prevent total destruction, the Spectre and the Living Tribunal created an amalgamated universe, in which only Access and Dr. Strangefate (Dr. Strangefate was a mixture of Charles Xaiver, Dr.Strange & Dr.Fate) knew the truth about the merge. The two characters fought against each other to reverse or preserve the change.
Access managed to separate the Brothers with the help of Amalgam's heroes; before the merge had taken place, he had planted 'shards' of the universe in Batman and Captain America. Once he discovered Dark Claw and Super-Soldier, he used those shards to give the Spectre and the Tribunal the power to restore the universes. Batman, Captain America and Access were thus able to make the Brothers realize that their conflict was pointless, and the universes were separated once again.
Dark Claw (Logan Wayne). An amalgamation of DC's Batman (Bruce Wayne) and Marvel's Wolverine (Logan).
Deadeye (Bill Lawton). An amalgamation of DC's Deadshot (Floyd Lawton) and Marvel's Bullseye.
Doctor Doomsday (Victor Von Doom). An amalgamation of DC's Doomsday and Marvel's Doctor Doom.
Doctor Strangefate (Charles Xavier). An amalgamation of DC's Doctor Fate and Marvel's Doctor Strange and Charles Xavier.
Lethal (Sergei Minerva). An amalgamation of DC's Cheetah (Barbara Ann Minerva) and Marvel's Kraven the Hunter (Sergei Kravinoff).
Nightcreeper (Kurt Jack Ryder). An amalgamation of DC's Creeper (Jack Ryder) and Marvel's Nightcrawler (Kurt Wagner).
Skulk (Bruce Banner). An amalgamation of DC's Solomon Grundy and Marvel's Hulk (Bruce Banner).
Spider-Boy (Pete Ross). An amalgamation of DC's Superboy and Marvel's Spider-Man.
Super-Soldier (Clark Kent). An amalgamation of DC's Superman and Marvel's Captain America.
Here is the link for the full characters: