When the first intrepid explorers set off 'into the black', they found that we were not alone in our galaxy: there were a variety of humanoid and non-humanoid races spread throughout space.
Fortunately, some of the nearby star systems contained planets that were, or could be made, habitable. From the large numbers of abandoned ruins the trailblazers found, it soon became obvious that we were the new kids on the block in terms of galactic civilisations.
Since the Earth was heavily over-populated and running out of resources, a large programme of spaceship building ensued. This was overseen by the recently-created Terran Union, which established a monopoly on colonisation.
A number of groups who did not wish to adhere to the policies of the Union, particularly towards the increasing numbers of individuals who exhibited psionic powers, decided to explore space independently.
One such group, known as the English Royalists and Nationalists (ERaN) stole three worldships and set off towards the centre of the galaxy. They reasoned, quite correctly, that the Union would concentrate on claiming and populating the systems near to home, which would mean that, if the Eranians, as they now labelled themselves, travelled a fair distance, they could get themselves firmly entrenched before the Union expanded far enough to attempt to annex them.
As luck would have it, they came upon a planet that had been a major centre of the civilisation known as the Forerunners, and among the ruins they discovered a massive fighting machine called an ogre, which was still functional.