Blade of Truth by Phil Kelly

Farsight is back! As the legendary commander comes out of retirement, can he deal with both a vicious alien invasion and the plotting of an ethereal to save his home? It's another action-packed tale from the master of the t'au empire, Phil Kelly.

Deep in the Vior'losan desert, an exile both revered and reviled lives a life of solitude. Farsight has retired his uncanny alien sword and bleeding-edge XV8 battlesuit so that his beloved enclaves can prosper in peace. But when the jaws of a tyranid bio-fleet close in on Vior'los, threatening to devour his adopted home, he must once more take up his blade in its defence.

As the tyranids consume the planet and its enclaves, however, an inside threat emerges in the form of the scheming ethereal Aun'Va, and the fortress world is soon reduced to its last eight warriors. Among them is Torchstar, a young rebel in possession of battlesuits prised from Aun'Va's iron grip, and as unlikely allies are thrown together in the dwindling hope of victory, Farsight's ultimate test is still to come.