Disclaimer: This is told from the antagonist's perspective.
3,000 years ago, we sent a probe containing a new, recently discovered substance to a new planet we discovered to study its effects on the environment. Due to little results, the project was abandoned.
Now, 3,000 years later, a species calling themselves "humans" have occupied this planet as their home, fleeing their broken homeworld. They have discovered our substance, calling it "mithril" and applying it to their militaries.They haven't even begun to comprehend its full potential.
We want it back.
We've sent an advance team of sorts: millions of our own wildlife, genetically reprogrammed to seek and destroy humans. They have largely been destroyed by the humans.
My war fleet is travelling at near lightspeed to the planet, which the humans have dubbed UBW-594244. We are bringing some new species along with us, the likes of which the humans have never seen.
They've had their fun. Now it is time to show them what it TRULY means to be our enemy.