Let's give Charon's Ferry another try. After securing power from the Light Seed, we find the ferry attended by what appears to be a Porobin Foot.

And functionally is. Weapons pass right through it, for whatever reason, but if you get close enough for targeting without stepping onboard, magic can kill it. This has no meaningful effect; the ferry activates on approach and will still work as usual.

After a short wait, the ferry reaches the far dock.

The Moon Temple is just ahead. Here we find a new monster, the Siren Grell (Marmablue), which is a floating jellyfish-like creature that likes to cast Absorb to steal MP. With any luck, they'll target The Boy, who doesn't have any to begin with. Inside, "Roses and Spirits", the sad town music, plays instead of anything you'd normally expect in a Mana temple, and there's just a nondescript starfield instead of a floor or other architecture. A U-shaped formation of purple flames marks the exit. The starfield loops forever in all directions, and there's little in the way of landmarks to help navigate. Siren Grells also appear here and there.

After wandering for a while, we come across a crystal orb. This one responds to Will o' Wisp's magic, and there's only one spell in that category that can even target the orb. One Saint Beam (Lucent Beam) later, the endless starfield fades out to be replaced with a more traditional temple interior, with violet flames and magenta stained glass. "Prayer and Whispers" plays, and the starfield area will no longer appear when trying to enter the temple.

To reach the orb quickly, just go up until you reach a Siren Grell, then left until you reach another, and the orb is just above that one.

The next room is the inner sactum already. "Eternal Recurrence" plays inside. The seed rests on its altar, and a glowing figure stands in front of it.

The Girl gets a spell that boosts attack power at the expense of evasion, one that guarantees critical hits for the next few attacks, and a saber spell that gives life leech (just be careful not to hit any undead/demon enemies with it). The Sprite gets Absorb. Also two other oddball spells with little practical purpose, but Absorb by itself is more than worth it, giving The Sprite effectively unlimited MP in the field. Just don't cast it on incorporeal enemies.

"Prayer and Whispers" now plays, and all that's left to do here is to gain the seed's power. It reacts much as the others did, its glow a bright yellow:    

Mana Energy is now 7.

The monsters outside the temple remain, curiously. Flammie won't come pick us up here, so we need to take the ferry back.

From this point on, I recommend leveling The Sprite's spells in the field, draining magic from enemies as needed. For The Girl, my preference is to head to the Wind Temple, where there's quick and convenient restoration right there in what's technically a combat area, giving full magic experience.

For anyone who may be struggling with the Moon Temple, Charon also offers a hint upon leaving without solving the puzzle:

Having ぷらねたりうむ (planetarium) set off in brackets and written in hiragana instead of the standard katakana representation (プラネタリウム) is suggestive of parroting a word as a special term without understanding its significance.

Another temple with no sign of a sage. Let's try back here once more.

We probably should have seen that coming. Is the sage ever here?

After we secure power from the Moon Seed, soldiers no longer block the entrance, and what's more, a familiar figure awaits us inside.

Gemma wanders off on his own, leaving us with a number of useless soldiers.

If he's after the king, maybe the throne room? The castle has a relatively intricate layout, but it's fundamentally just a big loop, with a bedroom and the throne room through doorways from a large chamber with a wide carpeted stairway. The king is inside, with a pair of slightly less useless soldiers.

Everything seems fine until we approach the king.

Well, that escalated quickly. Gemma enters before anything else can happen.

In a bit of lack of attention to detail, the king (?) does, in fact, have a shadow throughout the scene. The game may not be able to remove it.

The king (?) turns away.

Gemma and the soldiers vanish.

A boss battle suddenly starts. The Dark Stalker is essentially a souped-up Ninja, with Antimagic (Dispel Magic) to clear our buffs and charge gauge, Ice Saber instead of Flame Saber, the ability to sink into and quickly move around in the shadows instead of ineffectively hiding behind a screen, and a signifigantly higher tendency to swap weapons (which also makes the saber spell mostly pointless).

Dark Stalkers will appear as ordinary enemies not much further into the game, so this battle shouldn't pose any particular difficulty.

Although the king also remains in the room during the battle, there's no point in trying to talk to him...

...until after dealing with the enemy. The boss music fades out.

After a cut, Gemma and a larger group of soldiers are back in the throne room. "Seaside King" resumes.

Gemma has more to say.

Everyone nods.

He leaves. Might as well talk to everyone.

With the immediate crisis over, soliders throughout the castle are back on standby, and a number of civilians have also appeared out of somewhere. Some have interesting backstory or help fill us in on what's going on in the world now.

Others react to us directly, though only the first line seems like it might be important.

And one is a victim of inadequate proofreading in the English version:

In the same room as the above is an invisible passage in the southeast of the main area that leads around the edge of the room. A few other areas have passages similar to this, but this one is unique in that it actually goes somewhere, to a merchant on the eastern side of the bridge above.

Curiously, although the Tortoise Mail and Gold Bracelet the merchant offers aren't sold anywhere else, neither of them is even the best stuff sold here, and what you should already have from the Gold City outclasses his entire inventory. The bracelet at least provides protection against petrification, for what it's worth.

Speaking of local curiosities, the game has an unused line (part of an unused event that would have fully restored the party and offered a save prompt):

We'll finish out the area with a soldier found near the entrance.

The mistranslation is understandable; あらん (aran) looks like a negative form of a verb. However, あらんことを (aran koto wo) is a rather ceremonial-sounding equivalent to ありますように (arimasu you ni), using a fairly uncommon archaic volitional form. This line calls to mind similar religious blessings, like 神の御加護があらんことを (kami no go-kago ga aran koto wo, may God/the gods bless/protect/favor you). An even closer parallel is the line フォースと共にあらんことを (FOOSU to tomo ni aran koto wo), the Japanese rendition of "May the Force be with you" from Star Wars.

Note that you must finish the Darkness Temple before this scene will occur. As I previously mentioned, it's an interesting bit of non-linearity in the storyline. The Light Temple, Moon Temple, and Tasmanica events chain into each other in that order, but the Darkness Temple has no preconditions beyond being able to reach it, and isn't required for anything until this scene. If you've been putting it off for whatever reason, you'll just be told the sage is there until you clear it.

It's starting to seem pointless, but we should probably check back here once more.

The sage's cave... as in... here? Is this some kind of joke? A wizened old man with a fancy staff and long gray head and facial hair appears.

We'd better agree. Declining does nothing except making us listen to that again when we're finally ready to continue.

A passage deeper into the cave opens up to the side. Aside from a few Siren Grells, the passage introduces two new enemies. The Grenade Bomb (Nitro Pumpkin) may cast Sleep Flower, Burst, or Countermagic (Wall), and also has uncommonly high defense power, making it abnormally difficult to kill, though it isn't especially dangerous otherwise. The Shapeshifter (Shape Shifter), on the other hand, can turn into any of several different enemies, some of which don't otherwise appear until after we have significantly better armor, and can inflict frightening amounts of damage at this point.

A party wipe at any point during the trial does not result in a game over, but instead returns us to the sage.

The path is fairly linear, though it has a few short side branches that dead end. You'll need to use the Axe repeatedly to cut through stalagmites, and the Whip once to cross a gap about halfway through. Given how problematic the enemies here are, it may be best to just rush past them and to the far end as quickly as possible. Some of the Shapeshifter's transformations may drop advanced armor, but I'm not convinced they're worth the trouble.

Suddenly, we're attacked by... ourselves? Sort of, anyway. They have a different, more grimdark sort of coloration so that it's easy to tell them apart, but otherwise look the same, act much the same as computer-controlled characters, and have versions of the same starting weapons. They'll even use an onslaught of the same charged weapon attacks we can use, but that's all. No magic or anything similar. Speaking of which, even our most powerful magic barely scratches them, so we'll have to use weapon attacks, too.

Twinkle Barrier (Lucid Barrier) trivializes the battle, and with good armor, that might not even be necessary to keep them from doing any damage. And although most magic can't hurt them directly, Energy Ball (Moon Energy) works nicely to add damage indirectly by ensuring critical hits. Additionally, Evil Gate can hurt them, because it ignores magic defense, but its high MP cost makes it suboptimal.

Each doppelganger, upon defeat, nods as though in approval as it fades away. Leaving after overcoming all three returns us directly to the sage's chamber.

The old man is indeed gone. Zico steps forward.

He heals the party at this point. Well, that settles our next destination, at least.

The barrier that previously blocked entry is gone, and inside we find Emperor Vandole with Shiek and Faunach.

He looks at the other two. The one with the deep purple color scheme steps forward.

Emperor Vandole and Faunach continue ahead, leaving Shiek to confront us alone.

The scene shifts into a featureless square boss arena, and "Crisis" starts up as usual. Shiek has apparently turned into a giant monsterous... something... with an enormous toothy maw on the top of a globular body supported by two spikey legs that end in sizable tripod-like feet.

If you check the status screen during the battle for whatever reason, you'll find that Mana Energy is now listed as 0, and the seven seeds found so far all display in a dull, lifeless color, presumably to indicate that their seals have been broken. Much like when the Water Seed was stolen, Mana Energy functionally remains 7, so you still get a magic/effect bonus of +49 and can raise magic levels up to 7 as usual.

The Mega Xorn (Aegagropilon) will protect itself from spells with Countermagic (Wall). It can also cast Burst and Sleep Flower for significant amounts of damage and annoyance, respectively, and can get fairly spammy with both. The creature can also leap across the arena or roll around as a ball and cause more trouble that way. Party members will sometimes take damage just by touching the main body, which doubles as its vulnerable point, so long-range weapons are the way to go. Spells will also work after dispelling Countermagic with Antimagic (Dispel Magic), except that the Mega Xorn tends to recast it immediately. It does eventually run out of MP, which of course also disables its other spells, but has enough to start with that it will take a while for that to happen.

I suspect that it has an attack with no visible animation, and that's why touching it sometimes hurts but other times has no effect. In any case, stand back.

As with the doppelgangers, I'd recommend using Twinkle Barrier (Lucid Barrier) to block physical damage and Energy Ball (Moon Energy) for guaranteed critical hits. A steady stream of Antimagic will help keep it distracted while compelling it to waste MP recasting Countermagic. Better yet, The Girl can reliably sneak in a spell right after The Sprite dispels, and by staggering when they cast, The Sprite can follow her spell with Absorb (Magic Absorb) to eliminate its MP more quickly, or an offensive spell for damage. It's Wood element, so has no weaknesses or relevant resistances.

On that note, Mega Xorn uses level 7 spells, so if Shade is below level 7, it will take more than one Antimagic to completely dispel its Countermagic.

After the battle, we find ourselves back in the temple where we were before.

Did the boss fight happen in some sort of pocket dimension? With netherworld power involved, it makes as much sense as anything.

After the battle, an eighth Mana Seed, this one forest green but just as dull and lifeless as the others, appears in the Mana Energy section of the status screen.

Upstairs, we find the altar room, but the seed is already spinning on end.

And nothing happens.

An anthropomorphic tree appears at the base of the altar.

"Soul of the Night" begins playing as we approach the tree.

Dryad disappears, and the screen rumbles menacingly.

From atop Flammie, we see a large landmass rising out of the coral reef. The music when flying around has changed to track 28 暗黒星 (Dark Star), an ominous tune that portends war. Now that the continent has settled into place, we can land back at the temple, where "Dark Star" continues playing. It's now on top of a large structure rising out of the ground. Monsters are all around, and Gemma has arrived, too.

Trying to use the main entrance is indeed pointless, as the way in has been cut off.

Meanwhile, Dryad has given new spells to both The Girl and The Sprite, but each gets only two instead of the usual three.

The Girl gets Countermagic (Wall) to reflect spells (though be warned that it also reflects helpful magic) and Revive (Revivifier) to raise fallen allies. The Sprite gets Sleep Flower and Burst, which isn't a self-destruct spell despite how it works when some enemies use it. Burst has the most raw power of any offensive spell in the game, but can't take advantage of weaknesses, and it will need to be leveled up to reach parity with the spells you've had for longer.

In short, Dryad's spells are very situational, and it's going to take a while to build up their levels. There are reasons to get those levels anyway, though.

If the Empire raided the world's temples, maybe we should check in on Luka. Sure enough, the seed is spinning on end and there's no sign of her nearby. However, there is a small basement that seemed pointless earlier, and further investigation finds her locked inside a room down there.

She never does go back upstairs or resume healing and saving, though, and gets locked in again if you leave and come back. Seems like another oversight.

It would make sense for something to have happened here, too, but the only difference from before is the seed itself.

However, there is an unused condition lurking in the game data. If the variable that handles event progression in the Wind Temple is set well beyond any value it ever actually reaches, the music changes to "Holy Intrusion" and the old sprite gets different dialog:

Even by modifying the variable, though, that's all that happens. Anything more was either removed or never implemented to begin with. The other five temples just have their seeds in the unsealed state, without any lingering unused events at all, though they're all unoccupied anyway, so that's more understandable.

Other than the sage's trial, this whole chapter of the story feels weirdly abrupt and abbreviated. If armor progression is any indication, you were originally meant to go to Tasmanica after Mandara but before reaching the Gold City, so I could imagine seeking their help to breach the island. Possibly to reach the Moon Temple, too. Perhaps there would have been some forced back and forth, similar to the Salamander and Fire Temple event?

This is wild conjecture based on very little, but what if it went something like this: You first try to reach the Light Temple and fail to get very far, but find Wisp along the way. At that point, you're redirected to the Moon Temple, and have to convince the Sandship to ferry you across the Celestial Sea, or else stow away as it goes there on its own. After securing the temple, the Sandship receives an emergency message to return to Tasmanica, and brings you along. Then a more fleshed-out version of the Dark Stalker event occurs, and poses more of a threat thanks to happening earlier on. As thanks, and because Gemma is no fool, Tasmanica then helps you break into the Golden Isle, and Tasmanica's armor actually comes in handy instead of being outclassed before you can even get it.

Speaking of Tasmanica, early screenshots and promotional material despict a drastically different version of it, with around twice as much island, a walled town outside the castle itself, and some surrounding wilderness areas besides. It seems that housing everyone in the castle was another last-minute handwave.

After that, the main point of uncertainty is when you would have been given the ability to fly. Right before the sage's trial? As a reward for clearing it? It's possible the aerial escape from the Empire was what got you airborne all along, but maybe it was originally meant for the Golden Isle. Or perhaps the events at the castle would have come after a successful raid on the island, giving the anti-Imperial forces a victory to make the sham peace talk seem more plausible.

That would also make the Empire going around breaking all the seals fit into the timeline of events more cleanly. Recall that when confronting the Emperor in his castle, he says they're heading to the temples, but nothing actually comes of that until quite some time later, after overcoming the sage's trial. It would make more sense for the castle encounter to come just before the events in the Wood Temple instead, perhaps with some side trips to attempt to stop them elsewhere first, which would also make Luka being locked up in the basement more meaningful and explain the traces of unused events at the Wind Temple.