If you are searching for the Liber Imperium PDF, it typically refers to one of two different rulebooks associated with the Warhammer 40,000 The Horus Heresy universes.
: If a Custodes force is your primary detachment, any allied detachments must also have the Talons of the Emperor trait. liber imperium pdf
It seems you are looking for the PDF of a text titled If you are searching for the Liber Imperium
In short, the "detailed story" of Liber Imperium is not a linear novel but an epistolary horror narrative about the Imperium’s desperate, self-destructive attempts to weaponize the warp—and how those attempts always, inevitably, backfire. Warhammer: The Horus Heresy – Liber Imperium is
Warhammer: The Horus Heresy – Liber Imperium is a 176-page army book for the second edition, providing rules for Legio Custodes, Sisters of Silence, Solar Auxilia, and Divisio Assassinorum. Reviews highlight the book's success in balancing elite units while noting a reliance on Forge World resin models. For a detailed breakdown of the Solar Auxilia rules, visit Goonhammer