u/colinjcole

Astropaths serve the Astra Telepathica. Navigators, the Navis Nobilite. Both have their internal politics and, externally, exercise political power. Both enjoy political influence on Terra and their members typically have access to resources most Terrans could never enjoy.

Astrotelepathy, in some ways, is like a puzzle: figuring out how to encode and symbolize complex messages, and decoding those that you receive - "wrapped in such complex allegory, tangential metaphors and obscure symbolism."

From The Outcast Dead:

> Khaldun was special, an astropath whose skills in metapsychic cognition could transform confused jumbles of obscure symbolism into a message that even a novitiate could decipher. As the raw, urgent thoughts of the expeditionary astropath spilled into his mindscape, his borrowed power smoothed their rough edges and let the substance of the message take shape. Ibn Khaldun interpreted and extrapolated the images and sounds together, alloying astropathic shorthand with common allegorical references to extract the truth of the message. There was art in this, a beautiful mental ballet that was part intuition, part natural talent and part training. And just as no remembrancer of a creative mien could ever truly explain how they achieved mastery of their art, nor could Ibn Khaldun articulate how he brought sense from senselessness, meaning from chaos.

On its face, this might sound fun, but your direction connection to the warp also subjects your body to its horrors, which bears its toll. Also from The Outcast Dead:

> The curse of the Astropath was premature ageing, and Kai didn’t need Sarashina to tell him that he had lost the clean lines of his high cheekbones and his growth of fine, salt and pepper hair. Though he was in his late thirties, he had the appearance of a man in his fifties, at least. The face that looked back at him in the mirror – on those days he could face his reflection – was gaunt and hollow, with pinched cheeks and sunken eyes. Only the most expensive juvenat treatments could conceal the damage constant warp travel wreaked on a human being, and no astropath, even one of House Castana, was worth that indulgence of vanity.

Beyond the physical decay caused by their heightened interactions with the Warp, Astropaths also face mental strain: they constantly hear the undisciplined thoughts, random chatter, and wild emotions of others whenever they are around them. Astropaths learn "to tune it out, but it's always there in the background."

Plus, if you end up misinterpreting visions, you can cause significant damage... and you are likely to be held responsible. More from The Outcast Dead:

> All too often, a message could be distorted by the mental architecture of the receiving mind, and such misinterpretations were the bane of every astropath. In all his years of service, Kai had never yet wrongly interpreted an incoming vision, but had heard – as had all students of the City of Sight – horror stories of telepaths who had misread desperate pleas for aid or despatched expeditionary fleets to destroy worlds whose inhabitants were loyal servants of the Throne.

There are two other downsides, one minor and one bigger. First, the minor: that the position of Astropath requires completing a ritual of "soul-binding," connecting part of your soul to that of the Emperor. This shields you from many horrors of the warp, protecting you from corruption and daemonic taint - but also usually destroys your eyes, assuming your survive. However, Astropaths can see through their psychic senses, so this is no great loss.

The second downside is that soul-binding is not perfect, and powerful psychic backlashes can quickly extinguish the lives of astropaths. This is obviously a unique, unusual, exceptionally bad scenario, but here's what happened to Terra's astropaths after Magnus breached the wards around the Golden Throne:

> Five hundred died instantly as their minds were reduced to blackened cinders by a flash of supercharged psychic energy.
>
> Choir Primus shrieked in unison, each suffering the agony of a slow, searing psi-death. Fully aware of their brains being seared from their skulls, the astropaths howled like wounded animals as their higher functions were burned away, until their crazed autonomic functions spasmed and broke limbs, spines and fractured skulls as they literally thrashed themselves to death.
>
> Sarashina’s mental defences were among the strongest in the City of Sight, but even she strained to hold back this unknown attack, her layered wards like a levee pounded by hurricane-driven waves. A cramping pain seized her gut, and Sarashina howled. When the permeable wall between realities was torn aside by a starship’s warp engines, every psyker within ten light years would feel a measure of discomfort.
>
> ... But the choir did not die easily or quietly. ... >
> The last surviving members of the choir shrieked as geysers of light erupted from their scalps. Howling monstrosities and nightmare aberrations were carried on the light, searing their way into the material universe through living hosts.

Still, your life, compared to most humans in the Imperium, is relatively cushy, and you have an important position on whatever starship you are assigned to. You also may enjoy somewhat practical use of psychic powers - for example, you are taught to create wards in your own mind and you often have minor skills in ordinary telepathy.

---

Navigators, on the other hand, appear to have a much narrower set of powers: they can use their Eye to navigate the Warp... and that's about it, other than that their third eye also will kill most mortals it gazes upon. From Ahriman: Eternal:

> He had been born and trained his whole life to see the universe differently from other humans. Where they saw chaos in the warp, he saw tide and flow, meaning in abstract patterns, sanity in madness. His time in the Eye had pushed him further, had allowed him to see the inverted truth of the universe.

Though, might there be more to their powers? From The Outcast Dead:

> The Navigators were a breed apart from astropaths, and no one beyond the confines of the Navis Nobilite truly understood the full extent of their powers.

While the Astra Telepathica has political influence on Terra, the Navis Nobilite exercise significant political power. But, that comes with a cost. While Astropaths can easily walk welcomed amongst the mortal masses of humanity and their peers on a starship, Navigators face a problem: they're mutants, which are generally abhorred by the Imperium. Though they are granted much leeway due to their essential nature to the Imperium's survival, they live incredibly lonely existences, regularly shunned. From Ahriman: Eternal:

> It was a strange thing about Navigators, he had come to realise: they were bred within the narrow lines of their houses, cosseted and tutored and kept closed off from everyone else. Then they were sent out, usually alone, just them and the Great Ocean and the ships they steered through its tides. They were always shunned, often hated, and their only closeness was with a clan they would rarely see.

Worse still, a Navigator's job is to stare directly into the Warp - into Hell itself, and if the nightmares of an Astropath and their exposure to the Warp are physically scarring, it's arguably worse for a Navigator. More from Ahriman: Eternal:

> Ahriman had taken Silvanus from an Imperial ship, and since then the warp had worked on the Navigator’s flesh. Year by year, he had devolved further. His mind was now as unstable as his body. >
> ... >
> ... the Eye of Terror roiled and bulged across the sweep of space. To Silvanus it was an ever-shifting storm of colour and light. Stars blinked amongst folds of pink vapour that coiled into brief images of feathered and scaled beasts. Motes of light burst into golden cobwebs and dissolved into cold black. He could hear it, too. Not with his ears – or at least he could not hear it when he looked away. Sounds like voices carried on desert winds, the rattling crash of a sea breaking on stone, the shrill call of something crying in the night and the answer following. He knew if he looked away and back then the vision would be different; it always was.

And from Ahriman: Undying:

> The psychic beacon that shone from Terra was a Navigator’s cardinal point in the warp. No two Navigators perceived the warp the same way, even if they were of the same bloodline and lineage of training. Their third eye let them gaze into the warp, but what they saw there was a creation of their respective minds. Some saw a jungle, alive with shifting paths and the eyes of animals watching from patches of dappled shadow under leaves. Others saw whirls of colour and shape made from images of faces and insects blurred together. Silvanus never saw the same thing twice. Not any more. The warp was different every time he looked at it. This time it had become a black abyss across which grey-white images danced. The Astronomican was an arc of chalk smeared across the slate of the abyss. The storm was a fizzing blur in the distance, but it was closing on them, growing larger with every blink and heartbeat. He could hear it now too, scratching inside his skulls and vibrating his bones.

Both Astropaths and Navigators have unusual levels of power and influence within the Imperium, but also experience unimaginable horrors and are quick to be blamed when things go wrong:

> ... ' it doesn’t look good when a ship is lost. The Navigator’s always the first one people want to blame.’
> ‘Or the astropath,’ whispered Kai.

Which existence would you rather live?

The life of an Astropath, more welcome among your peers, but constantly inundated by the intrusive thoughts of others all while creating and solving complex puzzles from day to day, facing the physical threats of accelerated aging and the not-insignificant potential risk of being destroyed by surges of psychic energy?

Or the life of a Navigator: shunned by most you know, perceiving indescribable vistas both beautiful and horrific, pathfinding through aetheric seas, more physically safe due to not directly interfacing with the warp, but slowly going mad as you gaze straight into literal Hell for weeks, months, and years on end?