Journal Tactica: Prospero Burns – The Judgement of Valdor is a softcover supplement book for Warhammer: The Horus Heresy (Age of Darkness 3rd Edition). It expands the game with new background, missions, army rules and unit profiles built around one of the most pivotal battles of the Heresy: the destruction of Prospero, homeworld of the Thousand Sons.

Where earlier accounts of the Burning of Prospero focused on the confrontation between the Space Wolves and the Thousand Sons, this Journal reframes the conflict from the perspective of the Legio Custodes and the elements of the Censure Host that joined the assault on Tizca. It builds on the background first established in The Horus Heresy: Book Seven – Inferno, giving Custodes players a deeper look at the Ten Thousand's role in this terrifying, unprecedented clash between Space Marine Legions and the Emperor's own Custodians.

The book contains an extensive lore section detailing the Custodian deployment during the Burning of Prospero, illustrated with artwork and diagrams charting the course of the battle. Alongside the narrative content, it includes a complete Legendary mission recreating the Fall of the Domus Tenebri, pitting a large Legio Custodes force against the Daemons of Tzeentch.

On the tabletop side, the supplement introduces the Adjutorum Sodality, a new Legio Custodes unit that gathers specialist warriors such as the Vestarios, Blade Champion and Signifer into a commander's retinue. For Traitor players, the book delivers a full army-building supplement for the Daemons of Tzeentch, including a new Psychic Discipline and an Alignment of Ruinous Powers chart for building mixed daemonic forces devoted to different Chaos gods. Two new Solar Auxilia Cohort Doctrines round out the rules content, one for each side of the conflict.

A must-have addition for any Horus Heresy collection touching on the Thousand Sons, Legio Custodes, Space Wolves or Daemons of Tzeentch, combining rich narrative material with substantial new tabletop options.