Delios. Our only shelter from a hostile galaxy, the world that saved our nation and the lives of every living species in the Saliac. Alone and stranded in distant stars, our ancestors came together and surmounted the odds to make the world livable, and then to hold against the alien menace that wished only to devour us. It is here where the first allegiances were forged with the Magdetum, the Constructs, and countless others. It is the beacon at the center of our burgeoning empire, a testament to the untold soldiers who have given their lives so that we might continue to survive and flourish. It stands as a testament to the strength of our combined ability and will, able to topple alien empires and bring distant stars to heel. It is a declaration that the Dominion will not bend. We will stand firm until we surmount the odds, or are shattered entirely.
Delios is the capital of the Alech Dominion. It was one of the first worlds colonized by the progenitors of the Dominion, the human colony fleet that was stranded in the Saliac galaxy by the collapse of a natural wormhole. These colonists formed alliances with nearby native xenos and worked to make the planet livable- before terraformation, it had no oxygen in the atmosphere, an atmospheric pressure of 25 atm, and an average temperature around 149 degrees Celsius. The CO2 and H2O heavy atmosphere had to have much of the gas present siphoned, and oxygen added, to make the planet breathable and decrease the planetary temperature. By the end the temperature was already in the low 50 degrees celsius, and dropping the temperature lower was accomplished slowly over time, as it was already manageable with domed cities and high quality air conditioning. With that, the world was livable, and possessed an abundance of water, a very useful resource for the new colony. Everyone needs water, and it has many chemical uses.
Delios never hosted natural life. The human colonists of the Dominion were the first colonists of the planet. Arriving in 9973, the planet has been a Dominion colony under Dominion control ever since it was founded. No enemy has ever managed to land on Delios, but that does not mean that it's defenses are lax. Delios is certainly not the most fortified location in the nation, but the defenses would still be a nightmare to crack for multiple reasons. For one, though the planetary defenses are not the strongest in the Dominion, that standard is much higher in the Dominion than in many other empires. Lightly defended here means that only a few city sized islands were designed entirely as self sufficient fortress complexes with void shielding, space for millions of people, and giant, high efficiency farms. Secondly, you do have to reach Delios to try and crack it, and that's no easy task. The Dominion Home Fleet, based out of the system, is the largest in the Dominion. It has the best supply lines, quickest reinforcement times, and most supplies. Stationary orbital defenses are no slouches either- every planet has a cloud of orbital stations, many armed with point defense cannons and anti-ship weapon batteries. These worlds also have very large populations with very large percentages of enlisted soldiers, reservists, and likely willing volunteers in time of invasion. The planets themselves have even larger batteries of anti-ship weapons. Each planet has a smaller reserve fleet that can be scrambled in an emergency. Combined, it would take a concerted effort with a massive cost over the span of years or decades to take the system for any enemy close to the Dominion in size and power.