A nightmare empire, made up of a unique four limbed species that can be described as a cross between a moray eel and a giant ground sloth. They can naturally live for hundreds of years, and with a small bit of technological assistance, they can live for thousands.
In addition to a long lifespan, the Andromedans had a form of genetic memory long before they achieved sentience. As their civilization developed, they turned to technological enhancement of this ability, eventually allowing fully implanted memories and personalities.
With the combination of long life span, implanted memories, and other technological enhancements. An Andromedan consciousness can exist for millions of years. Although this ability has come with a cost. Their social structure has become fixed and stagnated, even if their technological progress rivals that of the Old Order, it hasn’t progressed much since.
A harsh caste based system has evolved between the lower, shorter lived classes and the longer lived classes that rule. Those in power endlessly clone themselves, implanting or transferring memories from one generation to the next, and eventually edit out limbs from their oldest incarnations, encasing themselves in cocoons of life supporting technology and information feeds. There, they focus on matters where the timescales measure in eons. To assist with matters in shorter time scales, they will create lesser clones of themselves, to fill out the lower classes.
Andromedans by nature are fascist, and have outright subjugated or annihilated the countless species that once thrived in Andromeda. Now, any non-Andromedans are little more than slaves that fill non-critical roles in the empire.
The long lived elders of the Andromedans have sent an expeditionary force to the Milky Way to prepare for a galactic collision 4.2 billion years in the future. Uncertain of what they would find in the Milky Way galaxy, an initial force numbering in the trillions entered a newly formed one way wormhole to the Milky Way, with many times that number directly behind them.
Their initial forays past their arrival point had them instantly at odds with The Remnant Order. The Andromedans, so used to dominating anything in their way, found themselves fighting with Remnant forces equal in size and technological sophistication to their own. The Remnants, trying to protect a number of client species reporting unusual attacks in their space, were brought straight into the path of Andromedan expansion.
Unfortunately for the Andromedans, and fortunately for the rest of the galaxy, soon after they arrived their forces were cut off by a premature wormhole collapse. The bulk of Andromedan forces, even some elders, did not make it through.
With that collapse, the expeditionary force was left without resources to continue a push that could have shattered the unprepared Remnant Order, and the fighting drew out into a stalemate. The Andromedan forces began to consolidate and build.
To complicate matters further, the younger Andromedans and slave species brought to bolster the invasion suddenly found themselves in a galaxy not under the rigid controls of the Andromedan Elders and a large portion of the force deserted, wandering the stars of the Milky Way. But the well prepared Elders planned for this too, and as the free Andromedans fanned out across the galaxy, so did their agents and spies, creating a web of information that would trickle back to the Andromedan foothold.