* How did Rune make it from the Esper Mansion to Motavia? Even with Ryuka, you can only travel within the planet you're on, and he didn't have a spaceship.
** We don't know that for sure. Lutz had his own cryo-chamber independent of Mother Brain in PSII; it stands to reason that Rune may well have had memories of Algo's ancient technology and where to find the old installations, which we already know are capable of autopilot (like the shuttle that Demi gives you just after beating Zio), and how to get himself to Motavia.
*** In PSII, Shir also manages to pull off the same trick if she runs off on Dezoris.
*** While we talking about crazy teleportation tricks, Lutz has little difficulty zipping the party back and forth from Noah. It looks like long-range teleportation is in the Esper bag of tricks, even if it's not in Rune's or Kyra's personal repretoires.
*** See GameplayAndStorySegregation. Rune also displays the ability to do a megaheal on Chaz (restoring all HP/TP/Skill charges) during part of the story, but in actual gameplay can't even cast a lowly Res-spell.
*** Maybe it's something he can only do when he's in the Inner Sanctum and close to the Telepathy Ball?
*** The Esper Mansion also seems to have access to the "Dew" perfumes; maybe he's using those.
*** Another possibility is he DOES know the spell and is capable of doing it when he needs to, but is unable to take the group with him, or it takes a lot of energy and he needs extra time to recover, or some combination. Basically, he can if he needs to, but it's just impractical and the spaceship is more reliable or straight up necessary for the whole group.
*** My theory is that he never ''needs'' to take the party anywhere. The group have their own vehicle, they can fly through space on their own, why does he need to complicate things by revealing his own bag of tricks? And he's not going to do something ''for'' his chosen Protectors if they can easily solve the problem on their own - that's just EccentricMentor 101.
*** Fanon holds that the Ladea Tower has something to do with Rune's interplanetary travel.
* They call it a forest of ''carnivorous'' trees, but what are they eating? Kyra is the only person reckless enough to just go there in person, nobody lives out there except Darkness minions and apparently they don't leave the tower, and the trees themselves don't have mouths...
** Maybe they have other means of eating meat, like flytraps? Carnivorous doesn't have to mean strictly man-eating, they probably live on biomonsters.
* What exactly is Dark Force's plan? We see that it's acting in three separate places (at least two at one time - Garuberk Tower was active before the group fixed Kuran), but the Profound Darkness breaks free entirely without its help. Obviously, the Aeroprism is a military target, but the Dezolian snowstorm and the combination of monsters, Climatrol meddling and Zio's cult have no apparent purpose. Is Dark Force just killing people for the sake of killing people? My own theory is that Dark Force is GenreSavvy enough to know that Lutz and Rykros are serious threats to the Profound Darkness, and if nothing is done, they might choose another band of Protectors, hence its attack against Dezolis and its search for the Aeroprism. The attack on Motavia still doesn't make any strategic sense, though.
** Zio's cult most likely had nothing to do with Dark Force, they're more like a pet project than a plan and it's not like they really ''do'' anything except sing his praises, guard his stuff, and creep normal people out. The worshipers are obsessed with Zio, but they're brainwashed, and recover immediately once he's gone (except for that one flailing guy). Having a cult is probably just Dark Force giving Zio an executive perk.
* The Aeropprism really only has one use, and that's to serve as a navigation beacon to Rykros. Dark Force doesn't need it, he already knows where it is and what it does, plus he already has minions there, but keeping the protagonists away from Rykros meant keeping them away from the most important knowledge in the story (namely that killing Dark Force is only a delaying tactic, and that there is a true root of the problem that can be dug out by mortal hands), as well as the Guardian weapons. The Profound Darkness only tries to break out once it's clear that Dark Force has failed, even though it's obvious that she could have done that at any point during the game, because Dark Force is supposed to be clearing her way to freedom. Once that's off the table, PD has two options: cower in her cell and wait another millennium for the next weakening of the seal, which means accepting defeat, or try to plow through the Protectors anyway. There's plenty of reason to interpret the final battle as the Profound Darkness's complete loss of self-preservation. She's been sending all of her most powerful, destructive emotions out of herself in order to break herself out of prison, and she's got enough of those emotions to support THREE Dark Forces. By the end of the game, she is ''well'' beyond giving a damn about getting free, even to the point of making herself mortally vulnerable.
** Consider also that she's one of only three figures in the game who can use the Megid technique even after those three Dark Forces have been drawn out of her, sent into the physical world, and killed. The Darkness is brimming with unbridled, blind rage to the point that all she can really do is throw herself at everything she thinks is between her and the universe outside her prison.
* There are ''multiple'' Dark Forces running around, all with a different method of achieving the same goal, and it's actually a fairly smart plan when you think about it. Dark Force ''never'' uses a direct attack on anybody as its Plan A because it knows full well what it is and that there are heroes out there who will come up and kill it if they know it exists, so it finds indirect means to get its job done, and its plan is to wipe out all sentient life in Algo by making the planets themselves ''uninhabitable''. Early on, Rika mentions that she lost contact with Wren, but she's only been alive for a year. This means that Dark Force has only been at its plan for a few months, but look at the damage it's already caused by the time the game started: on Motavia, earthquakes are destroying homes, quicksand is dividing towns and threatening to swallow them up, monster attacks are so prevalent that sea travel is basically impossible, and literally ''half'' of the Motavian population has been wiped out. On Dezolis, the blizzard is causing the Parmanians to starve and freeze to death, the Dezolisians are pushed to the brink of their survivability and openly admit they won't be able to survive at all if it gets any worse, a horrible plague is causing a zombie apocalypse that ''just so happens'' to be drawing the reclusive Espers out of their mansion, and there's a fully-automated weapons factory churning out advanced-tech weapons with no apparent wielder in sight. On top of all this, Dark Force has basically destroyed the environmental control systems beyond full repair; Wren and Demi are ready to help keep it running, but they know it won't last much longer. Dark Force has no way of knowing who Lutz is going to choose as his champion or who that champion will choose to bring with him to the battle to save Algo, and the only way to be absolutely certain that the Profound Darkness will be able to break out of its prison unopposed is to obliterate ''every single potential Protector'' before the big event. It didn't end up working, but the plan itself was a pretty good one; if not for Rune being at Molcum when Alys and Chaz came looking for Alshline, it would have gone off without a hitch.
** So their plan was to get the genocide out of the way before she broke free, so she wouldn't have to face Protectors? I suppose that makes a certain amount of sense, though it still lacks the obvious military utility of Seth's attempt at the Aeroprism - if there are five survivors of any race left, then the scatter-gun plan has failed. (Was the 50% thing in the Japanese version? I don't remember half of Motavia's survivors dying off in the English.)
*** The 50% thing is just in the game itself. There's only two Motavian towns, Molcum and Tonoe, and Molcum gets wiped off the map, so by definition that's half their population centers, if not strictly the actual numbers of Motavians in existence. Dark Force's only true goal was to destroy the seal so that the Profound Darkness could get free, and it's a lot easier to do that if there's no one left alive to protect the planets that comprise the seal. Interfering with the Aeroprism struck me as a last-ditch effort. Seth is ''already'' on his way to get it, but upon meeting Chaz and company, jumps to join the party; it implies that Seth actually went there (either unwittingly possessed or just Dark Force in human form) to ''steal it'' before the heroes could, and then Dark Force actually attacked once it became clear that that they knew how to use it. If you use the Talk function between opening the chest and stepping outside the Temple for the cutscene, Seth asks to hold it, and Rune flat-out tells Chaz not to let him.
** Also, it wouldn't be just any five members of any race, at least one of the survivors has to be someone who knows the oldest secrets of Algo. And Dark Force makes concentrated attempts on both of the ones we meet in game. Lutz, and the Archbishop at Gumbious. The Espers can't be infiltrated because they're highly sensitive to Darkness and have retreated into a Mansion built on top of the Elsydeon cave, the single holiest place on Dezolis, so Dark Force starts the zombie plague to draw them out; DF itself had no way of knowing that Lutz was not only long-since dead, but had a reincarnation on another planet altogether. Once Garuberk Tower falls, Dark Force basically hate-nukes Gumbious Temple and turns it into a crater... because it had no way of knowing that it had a friggin' ''underground bunker'' where the Archbishop was able to stay safe. One of the things that makes Phantasy Star IV such an excellent game is that, unlike in most other RPGs, the major villains aren't clairvoyant or hindered by "the plot says so" reasons. Dark Force is hindered by very mundane realities because it doesn't get out of them just by virtue of being itself, and what it primarily suffers from is lack of reliable intelligence, and lack of mobile agency. It's not even sophisticated enough to have legs until the third act.