A fallen hero, resenting death is roused from the paralytic sleep he shunned, in an ash-choked pit under a blood-red eclipsed moon. This is a hollow of rebirth, and the beginning of Astronomica. Before the gate leading out sits a strange figure in ancient terminator plate, awaiting us.
"Ah, fallen hero, inflicted as thou art, I bid thee welcome. Fret not, thou'rt dead no longer, for such sleep may never fully descend upon a corse such as thine. Oh, forgive me, I am Orbeque; an apothecary, though some call me the Necromatic. I carried thee out of the sea from upon which thy Chapter forsook thy body and left thee to rot. Only one of thousands, kenn'st ye, though thou art cut of a different cloth, so I am certain."
This is, as stated, Orbeque the apothecary. He seems to have been dragging up dead bodies out of the carrion pit for some time and setting them on the Path to Resolve, as we will later see the piled bodies of unsuccessful Astartes lying on the wayside.
"Lo, beholdest thou that fortress away upon the valley-rise? That is thy home and destination, for now. I promise thee every chance to return to thy Chapter, thou only needst ask."
We leave Orbeque and exit the shrine, traveling up the Path to Resolve, where we meet the maddened figures of other space marines, presumably some of the Inflicted that the apothecary brought out of the sea who gave up, falling prey to insanity. Our path climbs the side of a steep valley towards the fortress Orbeque indicated, but before the gate stands our first boss fight, the rot-crazed Astartes, where we see the terrible effects of the Infliction if left unchecked. Interestingly enough, it is possible to influence the nature of this character, as we shall disclose presently.
So after defeating the Rot-crazed Astartes we enter Orbeque's outpost, what will become our home base for the first part of the story. Here we find Orbeque again, along with four other characters; a dreadnought named Vestur, an undead guardsman by the name of corporal Stike, an Astartes whom we assume was once a Salamander and doesn't give his title and a Dark Eldar archon, locked away in a cell. Speaking to the Necromatic will either end the game or unlock the outpost, as follows:
"The noble Astartes without the gate, knew'st thou him? Oh, that's alright. He was Inflicted as thou, and I brought him from the sea as wert thou-- yet, I offered him release and he chose to remain without the gate for "A more worthy Inflicted" to take his place. So I offer thou this: Wilt thou so accept thy fate, or deny it? It matters not to me. Choose thou to deny, and I shalt find another in thy place. Such is my task."
Awaiting another Inflicted
You are then given two choices: Accept fate or Deny fate. Choosing to accept will continue the story, denying will initiate ending 0 abruptly on a cutscene that shows you preparing to stand guard over the gate to Orbeque's outpost, awaiting the next Inflicted and, as you'll find, your next playthrough.
In the pre-release demo, you automatically were given the "deny fate" ending, being given no option. The story will go on, Orbeque will find another Inflicted, bring him back to the Hollow of Rebirth and send them to defeat your past character. Whenever you finish on the "deny fate" ending, the appearance, loadout and even possible drops of the Rot-crazed Astartes in your next playthough are modeled on your previous character, including any item upgrades.
Inhabitants of the Outpost
Orbeque himself fills the double role healer and of offering level ups, along with a tidy bit of exposition.
"Know'st thou of the Infliction? 'tis a state in which an Astartes, such as were thy kin, enter a state of waking death, as it were, never to leave this plane until such time as is appointed them, and no wound, however grievous, may alter that time that none knoweth save himself alone. Sometimes, such is noted in the fallen, and they are "interred" as they so quaintly state, within the armoured sarcophagus of a dreadnought, thinking that such things are noble and only deserving of a warrior of the Carrion-Lord."
The unnamed Salamander is our smith. He offers repair and new weapons for purchase, the stock of which increases as you reclaim territory. Another service he renders is "Enforce your resolve", which at a gradually increasing price restores your max HP limit. The price will increment up from 1000 creds to a whopping 8,800, unless you find and bring him an Iron Halo, which, when repaired, returns the price to 1000 where it will remain.
The archon sells you poisons and buffs (don't ask me how he gets hold of them!), also offering a choice to join the purpose of a cabal, which he says will be arriving a Convergence at any time, he knows not when. It isn't known what happens when the cabal is joined, except you won't be allowed on board Guilliman's ship and most of the DLC is rendered useless.
This early into the game, Vestr and corporal Stike don't have much use, except the dreadnought's dialogue is suitably absorbing.
"So a little exposition then, thou'rt due. We are a damned legion, for in falling we each are privy to our own time of death, to the minute. Neglect and abandon plague our bodies, for we innately know that no disease or wound wilt lay us low 'til such time as fate hath decided.
"Within our legion are two purposes paramount; the first, to slay as many foes of the Carrion-Lord as we may before the end, and the second, to find our missing Lord, for that glory which shall never be must be returned to whence it came'st. To this end, I beg thee, entrust thy utter devotion, for without a Lord we damned remain..."
He encourages endings 2 and 4, and actually offers the occasional level up at the cost of exponentially lowering chaos resistance.