Battle for Helios is the seventh book in the epic 'Nexus' series, part of the growing Star Crusades universe that chronicles humanity's first steps away from Alpha Centauri and beyond. For a thousand years the Helions have predicted the return of the Biomechs and their hordes, and for a thousand years they have done little to prepare. The Prophecy of Fire has spread like a disease through every world, infusing fear to civilian and soldier alike. The Khreenk and Byotai are no strangers to this, but will they choose to ally in the coming fight, or will they turn back to old rivalries and fears? The attack on Eos proved the Biomechs had returned, but it is their relentless advance into the heart of the Helios system that marks the first stage of the war. Comet C34 houses innumerable surprises, not least being the mighty invasion Arks hidden deep inside its core. Every planet in the system from the capital world of Helios Prime through to the ancient ruined world of Spascia is now under threat of occupation, and the Helions will be unable to hold them back alone. Battlegroups from across the Alliance rush to Helios, along with entire divisions of regular and territorial Marines and their war machines. Trenches are dug, weapon emplacements constructed, and artillery sited at every key point that might be struck. Meanwhile, out in the vacuum of space wait hundreds of ships, each part of a complex web designed to defend the four worlds under threat. Even the full strength of the J�tnar and their exotic weapons are called upon and shipped out from their enclaves on Hyperion, Prometheus, and Hades. Back amongst the old worlds of humanity are Spartan and Teresa Morato, the unlikely leaders of a motley band of marines and aliens as they cleanse Sol of every taint of the enemy. They are not there simply to fight; they are building up a military force unlike any seen before in the Alliance. An army so far from the ideals of the Alliance that its very presence could threaten the very thing they aim to defend.