Dark Empire Saga is the second original story arc in Dragon Ball Heroes, beginning with the upgrade to Super Dragon Ball Heroes. It was later adapted into the second saga of Super Dragon Ball Heroes: Dark Demon Realm Mission!. It is preceded by the Dark Demon Realm Saga.
It is composed of several sub-stories:
Demon God Towa Saga
Cell X Saga
Demon God Buu Saga
Mechikabura's Decent Saga
Towa uses energy stolen from strong people in order to revive her grandfather Mechikabura, however his body is old and he cannot move well. Towa tells him to use the Dark Dragon Balls to wish for youth so that he can take revenge on Chronoa, however the Dragon Balls scatter. Mechikabura notices one of them as it heads away, crossing space-time. Towa decides to go and get it but Mechikabura tells her to wait, deciding to grant her Demon God powers first.
It is soon apparent that the Dark Dragon Ball ended up on Namek in Age 762 (during the climax of the Battle of Namek). The ball had fused with the tyrant Frieza, empowering him to the point that he could overwhelm the newly transformed Super Saiyan Goku - even without using his 100% Full Power. The Time Patrol realize that this is altering history for the worst, and so Future Trunks and Goku head back to deal with the problem. Goku teams up with his past self and the two attack the now full power Frieza together, as Frieza holds the two Kamehameha back Future Trunks quickly slices him in half and he loses the Dark Dragon Ball, restoring history to normal as Super Saiyan Goku defeats the non-Dark Dragon Ball Frieza.
However, Demon God Towa manages to collect the Dark Dragon Ball - though Mira is killed by Future Trunks during the process - and brings it back to the Demon Realm with her, where she meets Mechikabura, who reveals that he has summoned more Demon Gods to aid in the search for the Dark Dragon Balls.
Chronoa discovers two changes in history and decides to split into two groups, she goes with Goku, and Future Trunks goes with a new helper - who turns out to be Vegeta. Vegeta tells Trunks that he will prove he is the strongest, not Goku. Vegeta wants to get going immediately, but Chronoa tells him that they all must pose first, Vegeta ignores and tells her that they should just get going.
Vegeta and Trunks arrive back in time, and Vegeta gives Trunks a device from Bulma that can locate the Dark Dragon Balls. The device leads them to the Cell Games arena, where they see the Z Fighters defeated by Cell, who has a Dark Dragon Ball. Vegeta easily beats down Cell and then destroys most of his body with a Final Flash, shocking Trunks with his strength. Vegeta prepares to finish Cell but is suddenly attacked by Demon God Gravy before he has the chance. Trunks catches him as he is sent flying and then places the Potara Earrings he obtained from Chronoa onto himself and the unconscious Vegeta, fusing the two into Vegeks. At the same time Gravy and Putine discuss how great their Demon God power is.
Vegeks suddenly appears, striking Gravy and announcing his identity, Gravy attempts to attack again but he is easily knocked down by Vegeks, angering him. Putine states that they must take them down, as they may get in the way in the future. However both parties are surprised as Cell begins to undergo a dark evolution.
Cell using the power of dark evolution transforms into Cell-X, a hulking giant of a being with multiple Spider-like legs that dwarves Vegeks in size. Whilst Vegeks is focused on Cell-X, Gravy takes the opportunity to hit Vegeks from behind, knocking him to the ground. Happy with catching Vegeks off guard, he too is then caught from behind by an attack from Cell-X who swiped him to the ground, Vegeks having quickly recovered, suddenly attacks Gravy and they battle briefly before Vegeks is grabbed by Cell-X and both he and Gravy are crushed as the weight of Cell-X comes crashing down on them both.
With both injured and annoyed at Cell-X getting in their way of their battle, they briefly put aside their fight and attack him in unison with the resulting attack wiping out Cell-X for good. Suddenly Vegeks diffuses leaving Vegeta and Trunks separated once again. As Gravy goes in for the finish on the two Saiyans they are suddenly teleported away by Chronoa's magic as Gravy wonders where they went.
Meanwhile a battered and bruised Goku stands off against Kid Buu with numerous beings and a spaceship surrounding them.
Plot (video game)
Demon God Towa
In the animated trailer, Towa and her army bow to the revived Mechikabura as the Dark Dragon Balls are shown scattering. Future Trunks is heading back to Age 762 in order to prevent Frieza - who had merged with a Dark Dragon Ball - from killing Goku, he arrives along with Beat and Note, and manages to stop Frieza in time, causing him to lose the Dark Dragon Ball. However before they can get it it is taken by Demon God Towa, who had come to obtain the Dark Dragon Ball that had merged with Frieza, she then attacked with a giant energy ball. However the Supreme Kai of Time arrives and deflects the attack, having brought Goku and Vegeta along with her. Due to Towa's great Demon God power, Supreme Kai of Time gives Potara to Future Trunks and Vegeta, who fuse into Vegeks.
In the game trailer, later, in the present time, Demon God Towa invades Earth with her army. After decimating the area she is in she encounters the Time Patrol and their allies, and thus sends her forces to face them. Future Trunks, Goten, Vegeta and even Bulma deal with the many soldiers, while Goku and Beat face off with Towa, the two attack with a combined Kamehameha attack dut to no avail as Towa easily deflects it with her staff.
After defecting the attack, Towa's confidence fades as she notices Frieza - who has merged with a Dark Dragon Ball - arrive with Zarbon and Dodoria and thus she flees. The Time Patrol then prepare to engage the empowered Frieza in combat once more.
Cell infused with a Dark Dragon Ball defeats Gohan and Demon God Gravy faces off against him to retrieve it.
Demon God Buu
Demon God Dabura easily takes down Kid Buu (who has merged with a Dark Dragon Ball), but when Dabura is distracted Kid Buu absorbs him, becoming Demon God Buu. After Goku and Vegeta realize that they are being overwhelmed by the Dark Empire's forces, they then fuse into Vegito via Chronoa's Potara earrings in order to fight back them and later Demon God Buu himself.
- Goku (Super Saiyan) vs. Frieza (Dark Evolution)
- Goku (Super Saiyan), Future Trunks and Xeno Goku vs. Frieza (Dark Evolution)
- Future Trunks vs. Towa and Mira
- Gohan (Super Saiyan 2) vs. Perfect Cell (Dark Evolution)
- Perfect Cell (Dark Evolution) vs. Demon God Gravy
- Goku (Super Saiyan 3) vs. Demon God Gravy
- Xeno Vegeta vs. Perfect Cell (Dark Evolution)
- Xeno Vegeta vs. Demon God Gravy
- Xeno Vegeks vs. Demon God Gravy
- Cell-X vs Demon God Gravy
- Xeno Vegeks vs. Demon God Gravy
- Xeno Vegeks and Demon God Gravy vs. Cell-X
- Xeno Goku vs. Kid Buu
- Xeno Vegito vs. Demon God Buu
- Turles (Dark Evolution) vs. Dark-Masked King
- Beat and Xeno Vegeta vs. Demon God Salsa