Chernabog managed to stumble upon a dimension that happened to house several worlds which, to his joy, had alternates of several of his allies. He also discovered The Heartless during an experiment to create more shadow demons for his evil armada. Initial experiments only came up with these black, ugly cute shadows that could reproduce by swallowing the darkness in one's heart. Afterwards, Chernabog began to scheme on how to use them and expand their types/efficiency. But Zeus eventually got word of this and sent his recently created keyblade warriors to stop this evil invasion of the Friends and heartless. In the end, the High Council won, sent the heartless away to the other side, and began to set up keyblade schools for pure-hearted warriors like Terra, Ventus, and Aqua. But there was one keyblade master, Xehanort, who was not getting in on the program and instead began to become interested in the keyblade war itself. Eventually, Chernabog approached the corrupt warrior and told him a little secret.....the only way to open Kingdom Hearts, the heart of all worlds, was to create the X-Blade from two hearts of pure light and darkness. Xehanort soon picked Ventus, such a student with equal amounts of light and dark, as his apprentice, just so he could extract the boy's darkness from his heart, combine it with D.N.A from a little boy in the Destiny Islands, Sora, and create the evil warrior, Vanitus, to become his new apprentice. At this, he immediatelley pitted his former apprentice Ventus against Vanitas to forge the X-blade in order to open the door to Kingdom Hearts and begin another war, hoping to uncover the secrets of the first. Meanwhile, he also began to manipulate Terra into becoming a warrior of darkness with the intention of merging his own heart with a suitable, younger body that will allow him to survive long enough to see his plan come to fruition. Though he succeeded in possessing Terra, creating a new incarnation of Xehanort, he was defeated by Terra's Lingering Sentiment and later Aqua, which left him in an amnesic state while found by Ansem the Wise at Radiant Garden.
- Now a student of Ansem, Xehanort became increasingly obsessed with the study of hearts so he could regain some of his lost memories. To that end, he sacrificed his body in the process to Chernabog and the Friends, creating a powerful Heartless and Nobody. His Heartless assumed the identity of his teacher, Ansem, with the title of Ansem, Seeker of Darkness, while his Nobody took the name Xemnas. With this, the heartless escaped the other side to join their new leaders, Chernabog laughing in triumph at the return of his evil influence to this pocket universe.
- "Ansem" Seeker, with the aid of Maleficent of the Inner Circle, followed by commanding the Heartless to do his bidding and steal the hearts of many worlds. Late into his evil plan, he took Riku's body to regain a physical presence. Although his goal of reaching Kingdom Hearts was realized, the light behind the door to Kingdom Hearts destroyed him, causing all of the worlds he destroyed to be restored. However, in the events of Chain of Memories, Ansem was revealed to still exist and fought to take over Riku's body again, who continuously fought back...that is, until the Kingdom Hearts Encoder completely annihilated the last few vestiges of Ansem
- Meanwhile, Xehanort's Nobody, Xemnas, first appeared in Hollow Bastion to test Sora for his own agenda, on orders from Chernabog's will. As the leader of Organization XIII and master of the power of nothingness, Xemnas controlled the Nobodies in his own attempt to control Kingdom Hearts. In fact, Xemnas was really the corrupted nobody of Terra, trying to find a way to break free of Master Xehanort's control while also fulfilling his goal of gathering 13 possible vessels for Xehanort's heart to inhabit. He was finally defeated by Sora and Riku in the World That Never Was.
- With Ansem and Xemnas both destroyed to recreate Terranort, Chernabog declared that his genius work and relentless command of so many villains made him an obvious shoo-in for the Inner Circle primarily as The Evil Genius and The Dragon as a conqueror of dozens of worlds and creator of excellent plans. This was proven when Master Xehanort finally revealed his grand scheme to both the Keybearers and the Friends: to recreate the x-blade by gathering 13 hearts of darkness made from his own being and 7 hearts of light, and make both groups clash in a great fight that will inevitably cause the x-blade to be forged once more and cause the keyblade war to begin anew, thereby leading to Master Xehanort using the power of the x-blade to reconstruct the universe in his vision of perfect balance with him in control of the entire universe. This scheme has been helped so far by the Friends, who aided Ansem SOD in his part to recruit a Young Xehanort from an alternate timeline in order to gather the 13 hearts of darkness for Master Xehanort's plans. Despite the potential amount of souls that would result from Master Xehanort's scheme, even Chernabog is still trying to comprehend his minion's scheme.