Dominus

Dominus was born in an alternate reality, one similar to the Mirror Universe that Captain James T. Kirk encountered, but far more harsh.
His family tree is similar to our reality's Nick Ryder but with many notable exceptions. While he did marry Julie Lei and have children with her, the circumstances were entirely different. His Angelica and Olivia were a pair of violent twins that enjoyed preying on the weak. Including their younger half brother Jackson who was the product of Dominus impregnating Nancy Peterson and forcibly ripping him from her womb for Julie to carry. The universe they came from was much more violent and harsh. Which lead to Dominus adopting a very nihilistic world view. It was his 'nothing matters, so nothing should matter' opinions that lead to Julie hooking up with the Emperor of the Terran Imperium, Tiberius. 
Faking his death so he could focus on his 'Grand Mission', he was able to secretly build up a rather large force behind his shadowy presence. 
He was not around when Julie was merged with this reality's version of her, nor when Tiberius began to move his forces into this reality to take it over and expand the Terran Imperium. Instead, he came over and took over the old Pythus Sector, turning it into his personal 'workshop of horrors'. Jackson had stumbled onto it and took over the old Vella Cava Station that monitored the entry into the Pythus. But it wasn't until Jackson had taken Terra Alpha's entire government prisoner, including his father's counterpart that Dominus took notice.
Quickly absorbing Jackson's "Scions of Sol" into his own forces, he deposed his bastard son and abused the woman that he had grown to respect, Solara Cross. Branding her with his sigil all over her body. 
Since Jackson's defeat and the Alliance prisoner's escape, he had taken to expanding his plan and moving past the Pythus Sector. Thessia was one of the first planets to fall, thanks to his alliance with the race known as 'The Brethren'. He demanded that Pythus be his and he be left alone, otherwise he would decimate more worlds.
For as good and generous as Nick Ryder is Dominus is just as sadistic, twisted and greedy.
The only one that shares his particular bent is the Ajem'Dasis Master, Lady Bellatrix, with whom has has started a rather torrid affair with, the intent of which is to create true heirs to continue their mission, long after they are dead. The product of their union were a set of fraternal twins, incubated artificially and aged in a time dilation chamber with virtual education. Ophelia and Ian are the only living children of Dominus at the moment, although there are other Dominus's from other realities that still have their children from other women. But for now, Dominus has taken his daughter Ophelia as his heir, and Bellatrix has taken Ian as her's. With a new 'family unit' at his side, his dreams of conquest are much more attainable. 
The first time the galaxy 'met' his daughter, was when they attacked Emperor Kaikoa Lei and his wife on Earth and then proceeded to destroy Mars, turning it into a uninhabitable, broken world, and then his 'partner' and their son Ian, lead the attack that made Gorvan Prime another uninhabitable, broken world. 
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Dominus possess the means to travel between the infinite realities to swell his armies, torture his enemies and have the raw man power he needs. Although he has been working on a clone army, one that is entirely loyal to him without any notion of rebellion. Still, he is a nihilist and knows that his own power doesn't truly matter and that eventually he will be snuffed out just as others like him were, but he is focused on his legacy. Centuries after he is gone, he wants to see his impact on the galaxy remembered and feared. That he was truly the superior mortal being. That no matter how powerful other 'omnipotent' beings were, the Q, the Borg and others, he, a mortal man, self made and self improved was the destroyer of worlds and the Dominus of the multiverse.