I put this together for my raid group text but thought others might like it. Kind of a summary of the 15 voice over messages from Osiris's data crawler decoding saved log entries about the Veil.
Please chime in if I've got something wrong, or with more info!
The tldr on that lore is that some Ishtar researchers (from the collective on venus) were working on / exploring a moon of Saturn, started terraforming Neptune, got attacked while traveling from the moon of Saturn to Neptune.
Crashed onto Neptune, found the Veil. Didn't know what it was. Electromagnetic anomaly. No mass but a tangible surface. The first team of researchers to touch it all died instantly by way of brain death. It also immediately was causing problems with all the exos that were with them because of electromagnetic radiation.
They quarantined all the dead bodies while they built an outpost (with the help of SIVA). Ended up using the Veil as a power source somehow in the process, even though chiomi was against the idea (the logs are all from point of view of chiomi esi who was one of the researchers and most are about Maya sundaresh who was her wife)... Maya was in favor of making an outpost next to the veil...
Soon after vex attack. They had started fucking up Neptune the same way they did with venus. But the Veil seemed to have prevented it. In their attempts to work around the Veil, the vex created some sort of field to isolate the Veil but this field also effectively hid the outpost (which would become the city neomuna) from the outside world.
During the analysis of the logs Osiris begins to see similarities between Maya and himself in terms of how they became obsessed with their research (Osiris obsessed with the vex and time travel, Maya obsessed with the veil)
Later... Maya and Chiomi theorize all their exos died because the Veil affected the "clarity" inside of them (clarity as we know is basically darkness extract, but Maya and chiomi didn't know this as it was a braytech secret). They think the Veil interacts with clarity and overpowered them and erased their minds the same way a magnet can erase like a hard drive or a floppy disk. Maya believes they can reverse this and instead use the Veil to write consciousness back to exos (or anything else that uses clarity). Chiomi thinks it might work but has concerns about if it's morally right. Maya says they're past the point where morality matters.
At this point in the play back Osiris even further identifies with Maya. He also asks nimbus what he knows about how the cloud striders were created. Implication that the cloud striders were exos created by maya/chiomi using the Veil to write consciousness into brain dead exos
Later, they talk about SIVA and how it's similar to radiolaria (radiolaria is aka vex milk). This was another Bray family invention (and we all remember how the siva "virus" fucked everyone back in rise of iron). It becomes clear that Maya and chiomi were now working on combining disabled vex machinery with brain dead exos and using SIVA instead of vex milk but just shielding the SIVA nanomachines from the Veil radiation. Implication that this is how the cloud striders were created.
Chiomi and Maya create an interface to connect a human/guardian to the Veil. The design is like an orchestra of sorts. There will be a conductor who directs what they believe is an orchestra of minds inside the Veil. Chiomi thinks it's dangerous. Maya thinks it's the only way to survive.
Next entry: the interface didn't work right. Everyone who was connected to it died. Their minds were erased. Brain dead. Basically the entire research team outside of Maya and chiomi.
Osiris draws parallels to what they've learned about the witness and how the witness is actually a collection of consciousness of an entire race
The next log entry is entitled lakshmi-2 and Osiris freaks out a little.
At this point chiomi has removed herself from participating in any more experiments. As soon as she abandoned the experiments Maya started pulling brain dead exos out of cold storage/quarantine. She atarted using veil and Veil interface in reverse to start writing consciousness into brain dead exos. She re-creates lakshmi-2 off her own memories of lakshmi-2 but it also contains Maya's own self. This is problematic to say the least. (Reminder that lakshmi-2 eventually ended up back on earth as the leader of future war cult who was super xenophobic re: fallen moving to the tower)
Next entry: they get the Veil interface working and it doesn't kill everyone. It becomes clear that the Veil is some sort of web of consciousness. A collective consciousness. Like an organic version of the vex network. Maya is happy. Chiomi isn't. She feels that the Maya she knew and loved is gone.
At this point neomuna is a full city with an entire generation of people that were born there. Nimbus says they don't want to listen anymore. Osiris says "Obsession is a beast with long sharp talons. A beast that does not easily release its prey." (Direct quote.... also... my own note.... are they talking directly to the destint-obsessed players? Breaking the 4th wall?)
Osiris says he found a way out of the grasp of the obsession beast. "By losing"
Next log: things seems to be going OK but then Maya and chiomi's spot on the moon of Saturn (this moon is called hyperion) detects that the warmind has reactivated and has classified the location on Neptune as the nefele stronghold. Chiomi thinks that if rasputin can interface with their network and learn what they know about tue Veil, it will be certain doom. Chiomi sends stargazer (one of the first cloud striders) to go deal with the warmind. Taking lakshmi-2 with them (I guess this is how lakshmi-2 gets back to earth).
Osiris says it's clear then that stargazer is the one who redacted all information about the Veil and Neptune from rasputins memory banks (this was a plot point in the season where we were working with Ana and rasputin)
Later: Chiomi decides the Veil is too powerful and must be contained and hidden. They will attempt containment and close down the interface facility, but allow neomuna to continue to exist and flourish.
Next log: chiomi is losing it. She remembers how on venus the vex simulated copies of all of them and trapped them in a virtual hell. She wishes the Maya she loved was still around. She says it's time to let go. She reaches out to the vex. (Intentions unknown but maybe to see if they are willing to upload her consciousness back into a happier simulation of reality)
(The real tldr tldr) nimbus asks "what did we learn here osiris?" And he says
"the Veil is Darkness — the power of consciousness made manifest — as much as the Traveler is the Light, the power of the physical world. The implications are great. But so too are the risks."
Osiris seems bitten by the old bug of going deeper. There are no more logs but Osiris is able to sue the decryption protocols of the logs so far to explore the network. Finds a way into an archive of the vex conceptual mind. This is the vex entity thay created one of the first big bads back in destiny 1: the black heart of the garden. Comparing the vex logs to chiomi's notes, it's clear that the black heart was a vex attempt to recreate the Veil. But they failed.
He confirms that both the traveler and the Veil operate parallel to the laws of nature but in synchrony with each other. The vex were able to link the black heart to the traveler but this wasn't the connection the witness wanted (implication that the witness controls or directs the vex in some way to some extent).
Osiris calculates then that the connection beam from the Veil to the traveler created by the witness with our accidental help (he connects through our ghost remember) cut through the traveler shell to something inside. Something they're calling the pale heart of the traveler.
Osiris says that some current time Ishtar researches propose that the Veil and the traveler were possibly 2 part of the same "thing" or were effectively one thing cut in two. Veil is darkness, consciousness, memory, thought, feeling, logic. Traveler is light, physical reality, color, sound, movement, chaos.
I guess you didn't bother with any of the story lines then?