Keisar Ephes is the final antagonist of the Super Robot Wars Alpha series, he is the true ruler of the Balmarian Empire, although only making his appearance in the final stage for the final confrontation. He pilots a mobile weapon named after himself and is voiced by Ichiro Mizuki, one of the members of JAM Project (that sung the theme song of the game).
Once known as Augustus, a Psychodriver born from an ancestor race that sired both Humans and Balmarians. He becomes the core of the Gebel Guneden, a defensive weapon to protect the Balmarians from Gunbuster's STMC. Augustus has a female counterpart functioning the same thing, Irui.
To escape the STMC, Augustus and Irui along with their Guneden machines escaped Balmar along with the majority of ancestor race, those who remained on Earth became known as 'Humans'. Eventually, Augustus was left alone as Irui felt nostalgic and returned to Earth. Despite so, Augustus ruled his people wisely and worshipped like a God, becoming the Spirit Emperor.
Unfortunately, sometime in his reign, Augustus felt left out in the cycle of death and rebirth from the Ideon's Ide. Seeking to surpass Ide, Augustus left his throne and set up Ruach Ganeden to become a puppet to rule in his stead. However, his methods of surpassing Ide involves devouring the souls sacrificed in his name. The mass sacrifice empowered Augustus greatly, but it transformed him into a blood-thirsty, mad tyrant, akin to a demon lord. Soon after, Augustus changed his name into Keisar Ephes.
Throughout the game, Keisar Ephes presented himself as a seducting voice for the protagonists, offering them great, infinite power and bringing messages of despair. This message, however, did not bring the protagonists down.
After the Balmar Empire is destroyed, Keisar Ephes finally made his appearance. He plans to collect the souls of the heroes to become part of his power and eventually surpass the Ide, which now resided within the Ideon amongst the heroes. He gained upper hand, until eventually the heroes heard messages from their fallen allies amongst the souls collected by Keisar Ephes (including friendly ones like Musashi Tomoe or rivals like Char Aznable and Haman Karn), encouraging them to fight on. In conclusion, Basara Nekki and the Fire Bomber receives a new song (GONG, the theme song of Super Robot Wars Alpha 3) which lifts up the spirit of the heroes back. After an attempt to silence the song, which disturbs Keisar Ephes' source of power, the the battleship of the heroes blared the song through and Irui and the Ganeden returned to put an end to her fallen comrade. The song made the souls collected by Keisar Ephes react negatively and desert their master, enabling the heroes to finally defeat Keisar Ephes once and for all.
If the player fulfills the requirement for the downer ending where the events of Ideon: Be Invoked takes place, Keisar Ephes' plan is fulfilled. As the whole world is destroyed, the spirits of the fallen heroes are added into Keisar Ephes' collection of souls where he will abuse them for his own purposes and recreating the world in his image, instead of ascending to a higher level of existence and reborn into another world like in the OVA.
- Keisar Ephes' final attack, the End of Galaxy, is widely accepted as one of the most disturbing attacks in the Super Robot Wars series history. It involves swarming the target with tons of freakish souls and bringing forth disturbing images of war, screams and pain, ending in Keisar Ephes' hysterical Evil Laugh and the Earth split into two, destroyed. If the attack counts as a Dynamic Kill, the target is dragged into his Hell and killed in an explosion of blood.
- The rise and fall of Augustus into Keisar Ephes is likened by many with the story of Lucifer and his fall to grace into Satan.