The design of the Luminoth is clever. When you think about it, Samus is helping some moths turn their lamp on.
Each temple's Energy Controller also looks like a big lantern.
Aether is a "rogue planet" that does not follow a solar orbit. In theory this would make the planet's sunlight and weather rapidly fluctuate, yet it remains stable for all of Samus' visit. How can that be? Likely something to do with the Light of Aether, literally bringing life to the planet by maintaining its ecosystems despite Aether's rogue trajectory.
Upon entering the Agon Wastes, you'll spot the large structure on top of the main area, with a giant caterpillar statue on its side; scanning this statue will have your data suggest that it may be a warning to travelers. Turns out that the statue represents Amorbis, the game's first real boss, meaning it was really a warning for the player.
There are some things about the Space Pirate base that don't make sense at first glance. For example, we know that the Pirate operation on Aether was a very stealthy operation, so stealthy to the point that the Pirate expeditionary force on the planet was relying on a single transport ship making occasional supply drops for them. It seems impossible that such a major base on Aether could have been constructed with only a token force and one ship. But consider a few things:
Echoes features the Space Pirates utilizing some kind of Flashy Teleportation technology to move around the planet. Corruption also sees some Pirates warping, but it is explicitly Phazon-based; the teleporting we see in Echoes is that a beam of yellow light appears, and a Pirate emerges from it.
Near the end of the game, once you obtain the Light Suit, Samus can also warp around the planet using beams of yellow light. The log book data indicates she is making use of a Luminoth Portal Network.
There are two Luminoth Keybearer corpses in the Pirate base.
The metal gate leading into the base is stated in the scan data to be made of Luminoth materials.
The Dark Beam is found in the base, and it is not a Pirate weapon. It is kept in a secure, isolated chamber, and scan data indicates the Pirates found it and were studying it.
Conclusion: the Space Pirate base on Aether was a Luminoth base that they moved into upon making planetfall. With an infrastructure already in place, suddenly the fact they only have a single transport supplying them makes much more sense: it would only need to carry weapons, computers, and other makeshift portable gear instead of the kind of heavy construction equipment necessary to build a base from scratch. After getting themselves situated, they must have discovered the existence of the Luminoth warp network and found a way to breach it.
Space Pirate logs state their Metroids were freed by Dark Samus, but they don't attack her. Why? Because Dark Samus was formerly Metroid Prime. And Metroids are capable of attachment, meaning at her most evil, Dark Samus still has a place for her fellow Metroids in her Phazon corrupted heart.
Ing eyes are not visible in puddle form and they don't attack while in it. Even the Emperor Ing can't hit Samus with its eye closed, further suggesting it might be a vision problem. Why then is the Boost Guardian able to use it so offensively? It has taken Morph Ball technology, and it can "see" the same way Samus can!
Why did Samus go to Aether? Because the Federation received a distress signal from its marines. Why were the marines on Aether? They were chasing a signal they intercepted from the Space Pirates. How did they intercept that signal? Dark Samus destroyed the Pirates' jamming apparatus. What does Samus do once she's on Aether? She unlocks, defeats the guardians, and generally frees the way to all the most Phazon-rich areas on the planet. Echoes entirely worked out in Dark Samus' favor, as Samus dealt with the Ing while Dark Samus just strolled right behind her and snarfed down all the Phazon it could find. And if Dark Samus had not done these things, Samus would not have gone to Aether, which means the Ing would have succeeded in replacing Aether with Dark Aether, bringing about the total destruction of all life on Aether and the Luminoth. After Samus won, Dark Samus decided to step it up and just take over the Space Pirates so she could use them as Mooks.
The only time we ever see the Ing possess a deceased creature is when it controls the Federation troopers at the beginning of the game. After that instance, there's never any indication the Ing even have this power. But there is evidence they can possess non-living matter when it comes to the robotic sentinels in the Sanctuary Fortress. So what we see in the beginning of the game aren't Darkling troopers, but their Darkling Federation power suits. This even explains the zombie-like jerkiness of their movement.
Why did the Ing send the relatively-weak Dark Splinters to take the last Light of Aether from the Great Temple? Look at the Great Temple from afar - it's high above the ground, and only connected to the ground by towers and elevators laced with thorny vines. Since U-Mos could likely disable the elevators to block their entry, the Ing's only way up was to climb up the elevators' exteriors. Sure they would've loved to storm it, but they didn't have very good options for travel.
U-Mos' presumed control over elevators may also be why the Ing weren't invading from areas with stronger Darklings - he cut off their access. If they wanted to storm the Great Temple with say, the mechanoids from the Sanctuary Fortress, they'd have to make quite a long trek on foot first.
This is why it's such a good thing that Samus showed up when she did and shut down the Space Pirates' operation. If the Ing had managed to collect enough of a Dark Space Pirate brigade without Samus around, their access to technology such as jetpacks, skiffs, and battering rams would've allowed them to storm the Great Temple with ease.
The late A-Kul is a continuation of Metroid's Samus Is a Girl legacy, making the Champion of the Luminoth a woman. She seems to be an analogue to Samus in some ways.
The Bag of Spilling that happens at the end of this adventure, when Samus returns many of the Artifacts, power ups, and weapons she found on Aether to the Luminoth, makes sense in context: Many of these relics were tokens of friendship from the Chozo to the Luminoth, and Samus is reaffirming those vows of friendship. In addition, a practical reason to return all the weapons is to ensure the Luminoth can remain well-armed and prepared to defend themselves if the Space Pirates continued to raid their world after the destruction of the Ing. Samus is still able to reactivate the Seeker Missiles in Prime 3 because she had the data for them, and could reconstruct them with the right materials and parts that she took from various facilities during the course of that game, and even in Dread, she was able to acquire the Storm Missiles through her memories of the Seeker Missiles coupled with the absorbed powers of Escue's X Parasite.
The game takes place on Aether, a planet that is known to be a rogue body. This planet, alongside all others visited in the Prime saga save Hunters, suffered the impact of a Phazon meteor. Because Phaaze supposedly always targets a planet for invasion, it's very possible that poor Aether wasn't meant to suffer the impact, it only crossed in the way to an actually targeted planet! Poor Luminoth...
Not necessarily; a rogue planet once discovered would be easily characterized in terms of its vector, and such characterization would be necessary if anyone intended to visit it ever again — if you don't know where it's going, how do you expect to find it when you wish to return? Targeting it with a Phazon meteor then becomes an elementary problem in ballistics, such that hitting it on purpose is many orders of magnitude simpler than doing so by accident. (This remains true even when you consider influence from other bodies of significant mass; projecting the last known vector of the rogue planet would lead to any such bodies close enough to exert gravitational influence, and knowing the mass of all bodies involved would allow further extrapolation to find the planet's current position and vector. NASA has done this for decades with interplanetary probes; for the Galactic Federation, or whoever, to do so, would be so utterly trivial that their astrogation equipment would probably do it automatically.)
The Ing could have possessed Samus at any moment between her landing and her seizing the Energy Transfer Module. That, mixed in with Back from the Brink above, means that the Ing were defeated through sheer blind luck. Considering this, remember that Ing Possession generally makes the host more powerful. Imagine a horde of Ing overrunning the galaxy in a fleet of hijacked Luminoth, GF, Space Pirate, and (thanks to Samus' gunship) Chozo tech. With a possessed, even stronger than usual Samus leading the army. The galaxy wouldn't stand a ghost of a chance.
The threat the Ing pose, in terms of being able to possess/mimic organisms and use their abilities for their own ends, seems very similar to that posed by the X-Parasites from Metroid Fusion. But the Ing have one crucial and frightening advantage over the X: they can possess Metroids.
Samus gets the energy transfer module just a few rooms away from U-Mos. The Ing's victory and total destruction of Aether was only minutes away at best.
U-Mos was likely only able to hold off the Ing in the Great Temple because of the environment. He had barely a handful of Ing-immune Lightflyers indoors, and the most dangerous wildlife the Ing could possess were Splinters and War Wasps. If the Great Temple had been in an area with more dangerous creatures, such as Grenchlers or Ingsmashers, who knows how quickly the Ing would've gained the upper hand.
Come on, let's have a little faith in U-Mos. Besides the environmental factors, the guy is the chosen Sentinel of the Luminoth; he can watch the Ing's activity using Sentinel Crystals, and has a barrier that can deflectliterally any weapon in Samus' arsenal. Not only that, but if you scan the corpses of the Temple Guardians, you'll learn that Luminoth are no slouches in combat and can really put up a fight. He would've probably been fine... his sleeping Luminoth friends, on the other hand...
The Space Pirate lore scans are partial Fridge Horror and partial Fridge Hilarity, depending on your level of schadenfreude. Reading them shows how the Space Pirates got in over their heads by unknowingly interfering with the Ing, in what was supposed to be a simple Phazon investigation on a seemingly-abandoned planet. Then they met Dark Samus, who began stealing all their precious Phazon and broke their cloaking device. Then they were discovered by the Galactic Federation, who began pursuing them as well. This culminated in Samus herself coming to Aether and finishing off their operation. It seems like literally everything went wrong for the guys, and none of it was even their fault.
On the Pirate Homeworld in Corruption you can find a scan referring to the events of Echoes. It pretty much sums up the situation: "Surely, we are cursed."
On the other hand, we have the crew of the GFS Tyr. After following a single Space Pirate frigate to Aether, their ship crash-landed thanks to the chaotic atmosphere. They then discovered that the Space Pirates had an entire compound built, and thus prepare their own encampment to take them on. However, this encampment was overtaken by Dark Splinters, who slaughtered and strung up every last one of them. Like the Space Pirates, none of them could have predicted this outcome and it's hard to imagine being in such an awful situation.
The concept of Ing possession is the usual Brainwashed and Crazy trope, but a step worse. The Ing seem to fully replace the minds of the Darklings they possess, effectively ending their consciousnesses for the course of the possession. While it's written in lore that Ings can freely abandon their Darkling hosts, this never happens in-game, meaning the last memory of any monster Samus kills is of their own violent possession. Most wildlife on Aether doesn't even understand what the Ing are due to how recently they entered the ecosystem, making it all the more unfortunate.
Luminoth lore scans show that the Luminoth could become Darklings as well. It details how many Luminoth had to slaughter their friends and family - even children - or else they would be killed in turn. Additionally, many corpses of Luminoth can be found who killed themselves in order to prevent possession from the Ing in their last moments, even mangling their own bodies in order to keep the Ing from using their corpses (as seen with the fates of the GF marines).
In the official Q&A for Echoes it was revealed that the Ing's minds are like highly-intelligent sharks. Imagine your spouse or child suddenly turning into a raving beast bent on murdering you because of some dark fog appearing out of no where.
Before the second Dark Samus fight (taking place on a huge tower), you can look out the window and see two Phazon crates on a ledge. After the fight, a weakened Dark Samus falls off the tower. When you come back down, the crates are gone...
When Samus first lands at the Crash Site, everything seems relatively peaceful - she's alone on this eerie planet, completely unaware of the battles that have been fought. Unbeknownst to her, a Luminoth Keybearer corpse is in the very same room, though she doesn't find it until later. A chilling thought.
Really, all of the Luminoth lore from their most dire hours is low-key terrifying.
A-Kul, the Champion of the Luminoth, was the last Keybearer alive. She managed to write clues as to where her Keybearer comrades hid their Sky Temple Keys before being overpowered by the Ing. However, she died right on the Sky Temple's doorstep, holding onto a glimmer of hope until the very end.
B-Stl and J-Stl were mates who were both killed in the depths of the Agon Wastes. Their corpses are mere rooms apart (it sounds like J-Stl fell first), which is a heartbreaker for sure.
G-Sch watched as the Ing used their weak and small as meatshields against his blasts so their leaders could get some hits in. He applauded their ruthlessness before passing.
C-Rch went out in a blaze of glory, fighting the Ing with his bare hands once out of ammunition.
D-Isl was forced to self-terminate, lest he become a pawn of the Ing's possession.
Meanwhile, A-Voq was able to resist Ing possession through will alone, forcing the Ing to just kill her instead.
O-Lir was so skilled he couldn't be put down by the Ing alone, forcing them to possess Luminoth mechanoids to defeat him. He was central to the development of said mechs, and he acknowledges the irony in this.
The Emperor Ing being mutated by Phazon shows you how powerful the substance is in comparison. Even the mightiest of the Ing, masters of shapeshifting, are at the mercy of Phazon.
