"Knowledge endures. It awaits only the light of wisdom to craft it into the vessel of our very survival. It is the ultimate weapon, and I alone amongst our order know how to wield it..."
- —Inquisitor Thaddeus Hakk to Interrogator Sphisid Wor, at the Convocation of Calisi
Very little of Hakk's early career is known to his peers, as he came to the Calixis Sector already in possession of the Inquisitorial Rosette. He now serves with the Achilus Crusade in its attempt to retake the Jericho Reach.
Soon after joining the ranks of the Ordos Calixis, Thaddeus Hakk became embroiled in the machinations of the Ocularians, a Radical faction of the Inquisition obsessed with divining the future and thereby learning what enemies must be faced before they become too powerful to defeat.
For over a solar decade, Thaddeus Hakk moved amongst the unseen and silent courts of the Ocularians, mastering many of the arts of divination and uncovering many dire threats to the future of the sector. One such divination took Hakk beyond the Calixis Sector and into the far reaches of the Koronus Expanse.
In a cold tomb on a dead, windswept planet on the verge of the Egarian Dominion, Thadeus Hakk faced the phantom of a long dead alien species. In so doing, he defeated his foe and undoubtedly saved many lives, but he was changed, his powers of divination gone, torn from him at the climax of that dread combat.
The Inquisitor wandered the Expanse for several Terran years, descending into a madness born of his inability to see into the future. He could not return to his fellow Ocularians or to the Calixis Sector, and so he fell amongst the lowest of the low, the so-called "Footfallen" of the Koronus Expanse.
Some say that Hakk forgot that he was an Inquisitor for a time, or else was conducting such secret missions that his filthy, ragged countenance and the black light of insanity shining from his eyes was a highly-convincing charade.
Whatever the truth, Hakk strayed into places few have ever returned from, and came back possessed of dark knowledge gleaned from carvings pre-dating the birth of Humanity itself.
Somewhere out in the void, in some forbidden crypt, Thaddeus Hakk found a new source of knowledge. By uncovering the most obscure secrets of the past, he believed one could uncover the secrets of the future.
The further back he delved, the more patterns he perceived in the ebb and flow of history. What had occurred in the past would occur again, he claimed, and the portents were all around if only they could be read.
Hakk committed his theories to parchment and dispatched messages on sprint-traders heading back through the Maw to the Calixis Sector. He sought to enlighten his former peers amongst the hidden ranks of the Ocularians, to convince them of this new truth he had discovered. In short, he claimed, if the Ocularians wished to know the future, they must first know the past.
The Ocularians' answer was soon forthcoming, and it was not what Hakk had expected. An unnamed, but undoubtedly senior Inquisitor of the Ocularian faction dispatched a kill-cell to assassinate Hakk, who only just survived.
Though effectively outcast from the Ordos Calixis, Thaddeus Hakk still bore the seal, and soon established himself amongst the senior servants of the Achilus Crusade.
Since his coming to the Jericho Reach, Thaddeus Hakk has taken every opportunity to explore further his Radical philosophy, and the region has proved a fertile ground for his theories. He has established a network of Acolytes and contacts, and led dozens of expeditions into the benighted Outer Reach.
With the coming of Hive Fleet Dagon, Hakk sought to enact his wild theories, and claims to have uncovered crucial evidence that the Tyranids have visited the galaxy before, perhaps hundreds of millions of Terran years ago.
In seeking evidence to verify this theory, Hakk has learned of the existence of the Black Library of the Aeldari, and believes that forbidden archive must surely contain the key to how the Tyranids were defeated the last time they ravaged the galaxy.
He appears not to have considered that the Tyranids might not have been defeated then at all, and are merely returning to reap another harvest in an eternal cycle of seasonal devastation and regrowth.
In personality, Thadeus Hakk is driven to the point of insanity, yet grim and determined, and utterly focused on his quest for knowledge. He has visited Watch Fortress Erioch several times, and has addressed its Chamber of Vigilance.
He fervently believes in penetrating the most hidden depths of the past, and of uncovering every last scrap of knowledge to be found within. His increasing obsession with the Black Library is a matter of some concern amongst his peers, some of whom claim he is likely to bring down the wrath of elder powers if he continues.
He has no interest in finery or overt shows of power, and instead prefers to wear simple, utilitarian clothes. He often wears a battered, old armoured vacuum suit, suitable to protect him in the alien environments into which he delves.
He equips himself with the tools of the explorer, and is always well-armed. Inquisitor Hakk is often accompanied in his expeditions by squads of retained troopers, each a veteran of scores of dangerous missions, as well as a cadre of expert xenologists, archaeologists and historator-savants.
He owns several vessels, none of which appear on any registries as belonging to him, and it is thought that he returns to Footfall periodically, perhaps to consult the contents of some hidden repository of forbidden knowledge he is slowly building up.
To what end, none can say, but it is certain that the Ocularians want Inquisitor Thadeus dead. Perversely, a small number of Inquisitors, including some former Ocularians, have aligned themselves with Hakk, and a nascent faction -- the Antiquarti -- has come into existence.
Though yet small in number, the Antiquarti are an active force in the Jericho Reach, and one set to become increasingly influential as more forbidden knowledge is uncovered.
- Dark Heresy: The Radical's Handbook (RPG), pp. 104-110
- Deathwatch: Mark of the Xenos (RPG), pp. 77-78