Upon entering Axiom Prison, the Marauder remarks "A slave is not a man. A slave isn't even worthy of death." This statement can be reasonably interpreted in many ways until the Marauder kills Brutus, and derides the Lord Incarcerator as a slave driver; this strongly implies that he believes slavery and incarceration are fates worse than death—the Karui emphasis of facing death without fear and living/fighting with tenacious determination means that being robbed of the freedom to live, fight, and die on one's own terms would be horrendous. Consequently, the Marauder likely believes that those who have been enslaved cannot die with dignity, and thus are not "worthy of death".
Sekhema Deshret originally chose to seal the Beast rather than kill it when she had the chance. It's possible that she did this because she knew that killing the Beast would free the Jerkass Gods to subjugate and terrorize humanity once more.
The player starts off Act One with barely the clothes on their back and using cast-off gear to desperately survive against weak monsters and zombies. But in a very short period of time, they end up being able to take on monstrous beings, including a mountain-sized Eldritch Abomination, and by the time Acts Five through Ten roll around, they're routinely slaying entire pantheons of gods. However, this makes total sense when you consider some of the things Sin says to you in Acts Five and Six: Sin, Innocence, and all of the other "human" gods were once normal humans, but they ascended to godhood through sheer ambition and willpower, gaining the abilities of deities by just amassing that much knowledge and magical power. This, coupled with the fact that the Beast was a Power Limiter on the gods that forced them into slumber means that ultimately, the Exiles are on the path to becoming gods themselves, and that by killing the Beast, you've removed the limiter keeping you from becoming a god like Innocence or Sin.
Oriath's All Crimes Are Equal policy makes a lot more sense in Act Five, when you read the mythology around Innocence and Sin. According to Innocence's tale, Sin was burned alive for the crime of stealing a fish and threatening his brother into not telling anyone. If the core of your religion is built around a story where a god was killed for stealing a fish, it's naturally going to result in a theocracy of Knight Templars who run around exiling people for petty crimes.
The Syndicate building fortifications and bases inside The Beast is, at first, just a hilariously outlandish artifact of a League Mechanic being forced to show up everywhere. But then you remember that a lot of the Syndicate's power comes from manipulation of the undead. The Beast is a source of nearly unfathomable quantities of thaumaturgically charged flesh and bone, so them trying to establish an outpost in a place with this grim, abundant resource makes a surprising amount of sense.
In the Weaver Chambers, one can hear eerie moans, muffled screams, and there are humanoid bundles of silk squirming against the walls. Yup, prey for the giant spiders. Except that during the course of Silk's mission in the Chambers, you kill every last one of the spiders, including their "queen". What happens to their victims, still alive and unable to free themselves ? *shudder*
The dead don't stay dead, but rise up and try to devour the living. And one of the Karui stones mentions an infant dying and being buried. Which brings us to the idea zombie children and zombie infants...
The collapse of the Eternal Empire happened over two hundred years ago, meaning most of it should be buried, yet none of the ruins or artifacts (such as the ancient journal in the Sarn coffee shop) left behind look like they've been in decay for more than ten years (indeed, the Solaris Temple is stated to be kept pristine by housekeeping magic). What's keeping the Empire in a state of recognisable decay?
Turns out that it was the Beast, as a side effect of keeping the gods suppressed.
How many Exiles there even were? In the Lunaris Temple, we see whole mountains of bodies and rivers of blood, dead people by the thousand heaped up, not to mention all the monsters which also used to be exiles. Yet Oriath is a small island off the Wreaclast coast... banishing in such numbers, even for the most minor transgressions, it must have a serious depopulation problem, especially since a lot of exiles die on the way: there are dead bodies in the ship at the starting screen, and only two people survive even being dumped to the sea. The logistics of the whole thing also seem very complicated: exiles are thrown out at the Wraeclast coast and then fend for themselves, while Piety and her Blackguards presumably round them up again?
Considering where you start, I'm reasonably sure that your ship was wrecked in a storm.
Fall of Oriath opens up with the player activating a portal device leading directly to the Slave Pits in Oriath, with the gate being just outside of Highgate and the Scepter of God. Once the Templar got it set up, they probably just started teleporting in Karui slaves en masse, marching them to Sarn, and experimenting on them there.
The Karui Warriors have a tavukai (sacred prohibition) of not using any kind of projectile weapons, so much that Marceus Lioneye was willing to bet that his legion would be safe charging straight into the Karui formation (and he was right, although his fall was due to something else). But the Marauder has no such compunction, and can use projectile weapon with no problem at all.
The sacred prohibition was for Karui hundreds of years ago, and they were original Karui warriors and not the ones who had settled in or been enslaved in Oriath. The Marauder likely hails from a divergent sect that doesn't have the same prohibitions.
How are there Piety Miscreations in the Beast? Very little time has passed between the Exile defeating Piety and killing Dominus and the Exile entering the Beast, so even if Malachai did teleport some of Piety's old corpses when he teleported her to him, she had very little time to turn them into Miscreations.
Simple: Malachai knows far more about thaumaturgy and Virtue Gems than Piety. He made the things. Or his proxies/puppets did.
It's implied that some time has actually passed in-universe from when Piety was defeated and taken to the Beast and when you arrived. Her dialogue regarding the Godless Three indicates that they spent quite a bit of time experimenting on her, so that gives plenty of time for Malachi to gather up more bodies from her workshop, since he's pretty much a Reality Warper who can create portals wherever he wants.
An obvious case of Gameplay and Story Segregation, perhaps, but how exactly do the gem slots on the passive skill grid work? Does a character just sort of reach into their inventory, grab a skill gem and sort of... magically slot it into what we're presumably meant to assume is a videogame abstraction?
One explanation could be that they works the same as a normal virtue gem, weaker, but without the need to slot them into equipment; all one needs to do to make use of the gem is devote some time into focusing the gem, then having it on their person. Another is that because it's the only thing the exile never takes off, their underwear serves as the "equipment" providing them with their almost certainly supernatural skill bonuses, and the skill gems work exactly as the rest of the gems do by slotting into their underwear instead of armor or weapons. Gems are weird.
The vaal experimented with implanting gems into people's bodies. It's likely you are doing a less extreme version.