Dromid

Dromids are a race of super advanced dromeosaurs, they have attempted three times to invade Rathnir and Eldham, but all three times failed horrifically with only one survivor out of the three, Dr. Sue Ironclaw.

Early History
In another universe far away, humans recreated dinosaurs at around the same time they were going extinct, they taught the new born race how to carry on the legacy of humans, and not to make the same mistakes as them. Their first leader made a blood promise to their teacher to NEVER let Earth get harmed again.

After that they only built in ruins and gained technology rapidly as they learned from the humans left overs, and they went from stone age to nuclear jets in only 2000 years. They migrated their entire population to a terraformed Mars where they prepared to conquer the rest of the solar system. After 5000 years since cloning they developed technology hidden deep in the depths of history, warp cores.

After 6000 years since cloning they had traveled to other worlds far beyond Earth, and made first contact with alien life forms, purple grass on the surface of proxima centari B. They found all sorts of life and kept on with their journey through the galaxy.

7000 years after cloning they met their first intelligent species, but they were aggressive and tried to kill them, but then were incinerated by nuclear warheads.

The Boring Parts
After their early history their advancements slow down, a lot. The only thing they discovered in space travel was how to go between universes, and so they just got bigger, but as they go along they found ruins, in multiple universes, of the same civilization. They concluded there was another like them, but they are now dead, long dead.

Now
Their empire is crumbling, but their promise will never be broken, in fact the rebellion leading to the fall of the empire says they broke the great promise as it is called.