Starro the Conqueror is a villain in the DC Universe and a Knight of Starro.
The being known as Starro the Conqueror was once a little boy named Cobi who lived peacefully along with his people (specifically his brother Andrez) on the "unremarkable" planet Hatorei. The Hatorei people lived simple lives and they had few semblances of a developed world but in one respect they were unsurpassed. Once a day the planets inhabitants would congregate in a species-wide telepathic link and open up to each other which made their society the pinnacle of ethics and cultural stability.
However, on a particularly harrowing day, a Starro Motherstar descended on their planet enslaving their civilization including Cobi and Andrez. At that point in time the Star Conquerors were only nomadic predators who wandered conquering planets until the Motherstar landed and birthed a new queen. So the Hatorei slaves served the queen and built a nest for a new queen to be born. On the planet Hatorei, things were different; the link between the people was still existent and it was impossible for the Star Conquerors to completely control the people. The link between the Hatorei was filled with outrage due to their enslavement and the deaths of their people; this outrage loosened the hold of the Star Conquerors on Andrez. So while Cobi worked in the nest, his brother driven by his peoples' outrage entered the nest determined to destroy the Starro hatchlings before a new queen could be born.
Unfortunately, one of the eggs hatched and the hatchling desperate to protect itself used Cobi to defend against his brother's attack and in doing so led Cobi to kill Andrez. Afterward, the force that drove Andrez (the collective outrage of his people) seemed to enter Cobi who then, having been driven mad by that force, ripped the Starro off his face regaining his independence. The hatchling attacked Cobi but to no avail as it leapt it became attached to Cobi's chest and Cobi subsequently destroyed the remaining hatchlings declaring that every Star Conqueror would be his.
Now Starro the Conqueror, he used his control of the Star Conqueror species to begin a series of war of conquests. While he would enslave most foes with Star Conqueror starfish, he would grant some particularly useful opponents larger starfish to wear upon their backs and a place at the head of his armies under him, allowing them free will so long as they turned their talents towards his conquests. As his empire's expansion continued, he was able to draw power from everyone so controlled. Between his mind-controlling staroos, ever-growing strength and his still independently thinking elite, his forces were unstoppable, leading him to gain control of nine galaxies.
Upon his forces reaching the Milky Way, Starro took control of L.E.G.I.O.N.'s robotic forces and uses their widespread galactic influence to further his goals towards dominating the universe.