Jaghatai Khan: Warhawk of Chogoris

As the Great Crusade burns across the stars, the primarch of the White Scars, Jaghatai Khan, must decide where his true allegiance lies.
Ever since the Imperium's rediscovery of the world of Chogoris, the White Scars' culture of warrior mysticism has sat uneasily with the ideals of Unity. As the Great Crusade burns across the stars, their enigmatic primarch Jaghatai Khan fights to preserve his Legion's distinctiveness amid a galaxy where cold rationality holds sway. Despite his self-imposed isolation, others in the brotherhood of primarchs seek to draw him into the greatest ideological battle of them all: the place of psychic power within the Legions. As the Librarius project is born, and opposition to it grows, the Khan must decide where his greatest allegiance lies – to the Imperial Truth, or to his own heritage.
The Horus Heresy: Primarchs
Series contains 18 primary works and has 18 total works. Current series reading order on below.
It's the start of a brand new series of 18 books focusing on the greatest of heroes, the primarchs themselves. This volume kicks it all off with a tale of Roboute Guilliman at the height of his powers, leading his legion into battle at the apex of the Great Crusade.
Main series Warhammer 40,000: The Horus Heresy