Due to the nature of the Slavs having no writing system prior to Christian rule, and the only accounts of Chernobog being from Christian sources, the history of this deity is difficult to define accurately or validate from various sources. He became known during the 12th century among the Western Slavic tribes, meaning he was either not important or a "new" deity. In addition to this information, Belobog is not mentioned in the Chronica, an account of Slavic gods by a German monk, and Belobog isn't mentioned in any historic sources that describe the gods of various Slavic nations/tribes.
Chernobog is a Slavic deity, whose name means Black God. Chernobog is not often mentioned in Slavic pagan sources, but is mentioned by the Western Slavs. He is associated with destruction, darkness and the winter. Due to this, he wasn't worshiped but instead avoided, just like Baba Yaga - This conflicts with the Slavic pagan customs of pleasing gods/goddesses and spirits in order to gain their blessing and protection. He is also synonymous with evil and later became synonymous with the devil.
Chernobog appears as one of the challenges of the game. After the player defeats Betelgeuse in the arena and goes to the Gaian Temple, the owner will ask him to convince a demon to join the temple so that they can punish the rebels. If the hero accepts, he can find Chernobog at the South District of Valhalla and defeat it at the entrance. After his defeat, Chernobog can be found at the Gaian Temple and will heal the player if they are not Law aligned.
"The god of death in Slavic creation myth. His name means "black god." His various domains include night, darkness, destruction, and death. Chernobog is the enemy of Belobog, the white god of light. Although Belobog and Chernobog rule over opposite domains - day and night, white and black, good and evil - they were initially friends who worked together to create the world from the mud at the bottom of the sea. They later became enemies, and after a long battle Chernobog was thrown down to the earth and became a spirit of evil. Chernobog's ability to cause bad luck has led people to invoke his name when putting curses on others."
—Shin Megami Tensei IMAGINE Compendium
Chernobog acts as a miniboss within the instanced boss area of Zoushigiya Cemetery. He also appears as support for Samael in his boss room within the Shinagawa Catacombs gold instance and as a nightmare variant within the Nakano Stone Site gold level instance. He can only be acquired through fusion.
Chernobog appears at the end of the Challenge Quest, Phantom of Madness, after the last Insane Horde is killed. He is the demon leading them in poisoning the area and is surprised that humans aren't so fragile as to be wiped out by poison as he dies.
"The god of night, evil, and death in Slavic lore. His name means "black god." Like many other gods of the dead, he is said to live below the earth. His counterpart is Belobog, the "white god." Despite being feared, he was also worshipped. The curse, "May the black god kill you," is still used in Ukraine."
—Devil Summoner: Soul Hackers 3DS Compendium
Chernobog is one of the rare Reaper demons, and must either be fused or can be encountered in the Corridor of Time. His Empty Wave skill makes him a deadly physical fighter.
In the 3DS remake, a variant Chernobog is available from Nemechi, unlocked at the leg stage of the female growth path. He costs 150 D-Souls and uses his artwork from the first Devil Summoner installment. While this version has both Tetrakarn and Makarakarn, his agility is too low to use them effectively, making him more useful for passing them on in demon fusion.
Devil Summoner: Raidou Kuzunoha Vs. The Soulless ArmyEdit
Chernobog is summoned by Rasputin to stop Raidou Kuzunoha the XIV from continuing his investigation. The Chernobog creates eight weaker copies of itself which must be defeated before the main one can be taken out.
Chernobog appears as a minor boss encounter. In battle, he summons two copies of the characters through their shadows with his skill Calamity and then joins with his sword, making him invulnerable. The shadow copies have the same skills, strengths, and weaknesses as the originals, but more HP. Chernobog will not rematerialize until the two shadows are defeated, at which point he can be attacked.
"The god of night, evil, and death in Slavic lore. His name means "black god." Like many other gods of the dead, he is said to live below the earth. His counterpart is Belobog, the "white god." Despite being feared, he was also worshiped. The curse, "May the black god kill you," is still used in Ukraine."