Underground Sewer 
Upon entering the cave that Frog opened by slashing it with a sword, a friendly bat joins us, and promptly flies away upon battle.
First off, the Masamune is a huge upgrade over Frog's last sword (the Iron Sword way back in the very first dungeon), and considering all the hoops we had to jump through to get it, it should be used here. Also, the Hero Medal can now be equipped by Frog, and it boosts the critical hit rate of the Masamune to around 50%. Not too shabby!
These are the only two enemies here. The Vamps are bog-standard beyond low magic defense, while the Gremlins are bog-standard beyond very high physical defense.
As expected, magic is the way to go here.
This is the game's way of saying, "You know, you've got a new character who's capable of learning magic, so you should do that."
So let's do that.
Also this is Frog's first trip across time. Considering he's a giant sentient frog, he's probably rolling with the punches.
Frog picks up his first spell, Water. It's identical to Marle's Ice spell in all but animation, though Frog doesn't have the Magic stats Marle and Lucca do. It's OK though, it'll be more than adequate, plus it means that Frog can start learning other Techs, plus this will unlock a few Dual Techs soon enough.
But before we kill the big bad let's visit home.
Crono! How many times have I told you to keep your pets outside!!
I am NOT a pet! Though I am...odd of figure, I am a master swordsman!
I'm terribly sorry, uh, Mr. Toad! NO! Mine name is...
......
I like how utterly nonchalant people are about giant talking frogs, no matter the era. Then again, there are far stranger things out there.
Anyway, here's Water in action. It's your bog-standard single-target magic spell.
But since we got a battle off with it, Crono can now combine that with his Spincut to do the Dual Tech SwordStream. Nothing with Lucca, unfortunately.
Underground Sewer 
And with that, we've got business to attend to. Expect a lot of character swapping for this update.
This adds 25% to the damage of Spincut and Water, making it the equivalent of Ice Sword and Fire Sword. Of course, if you have Marle or Lucca in your party, their higher Magic stats will add more damage than this. Still alright though.
Ice + Water = Ice Water. Surprising, I know!
It basically combines the damage of the two spells, so no extra damage for this one, but to compensate it affects all enemies.
This is actually pretty good for regular encounters and ends up being very useful in the next dungeon.
This one is a bit misleading. Basically, the Juggler will strengthen their guard against whatever they were attacked with last. But more about that once we meet them.
It's been a long time coming, but we've finally arrived.
Here we go...
SILENCE 
Magus certainly got the ambience down. The complete lack of music and sound makes things even more haunting.
...but not as haunting as the random people wandering around.
The left branch is a dead end.
The right branch has some more weird faces, and a few familiar ones...
Someone close to each character shows up here. This one varies, depending on your third character.
For Lucca, it's her father, Taban.
For Marle, it's her father, King Guardia.
For Robo, it's his father, Lucca.
Frog has Queen Leene...
And Crono has his own mom.
Alas, this is also a dead end. But upon visiting both rooms, this save point suddenly appears...
Confusing Melody 
...but all is not as it seems. This is where the music kicks in, and simple as it is, boy does it work for this place.
Magus is a tad busy right now. You'll have to take up your business with me...
You'll have to defeat all 100 of the beasts in Magus's castle...!
To be fair, you don't have to actually beat all 100. But interestingly enough, there indeed are 100 beasts in this castle.
These Henches are still Henches. They're weak to Fire but otherwise unremarkable and die as easily to Ice Water as anything else.
Magus's Castle is your first real test. This place is long, with lots of fearsome and tricky foes.
There's now monsters roaming the area.
Omnicrones are immune to all elements. Decedents absorb Shadow magic, but have no magic defense, are weak to Lightning and Fire, and have very low HP on top of that.
Up here the skeletons are busy stabbing each other.
Mainly I'm showing this because I love this line. Words to live by.
Anyway, this is where all those NPCs ran off to.
I really love the foreboding atmosphere of this place. Spooky skeletons fighting each other like morons, creepy music, the whole point is to build up the threat of Magus, albeit with a bit of comic relief here and there so it doesn't get too somber and serious. This is Chrono Trigger, after all.
This is Slash, expert swordsman and one of the fiends guarding the castle.
Naturally, Frog treats him with the respect he deserves.
You'd be singing a different tune if Cyrus hadn't been there with you last time!
Boss Battle 1 
Slash isn't too bad, though he takes half damage from all elemental attacks, so Lucca's bad for this fight. Robo or Marle are better, depending on whether you want to focus on offense or defense.
He has some moderately threatening physicals, nothing too scary.
X-Slash works well here.
Slash only has 3200 HP, so this goes by quickly.
However, we ain't done yet.
Slash has another 5200HP to burn through, but now is immune to Water and has slightly higher magic defense in general. Strategy should be the same as before.
With his sword, Slash has more powerful offensive options. For instance, now Slash can use Slash, which works like Crono's Slash, except this is Slash's Slash. Unlucky positioning can mean two or even all three party members can get hit with it, though the damage isn't too shabby, around 50HP or so.
He can also use Crono's Spincut, which hurts quite a bit.
And it wouldn't be a proper boss fight without everyone's favorite move.
It came down to Lucca throwing Tonics and Mid Tonics while Crono and Frog X-Slashed Slash. Turns out two Slashes are better than one!
And that's it for Slash.
Confusing Melody 
Our reward is a save point and the Slasher, a blade for Crono. It's a minor upgrade except for the really nice +2 Speed it gives.
Next, the right path.
FINE i'll play with you guys BUT THEN I GET THAT TREASURE OK!?
The Barrier is basically an item version of the Shell buff from the Final Fantasy games. However, it's weaker in Chrono Trigger because it only reduces magic damage by 1/3. Still, not too bad for magic-based fights, which I get the feeling we'll be dealing with soon enough.
Now our family members want to murder us. I show Guardia here as he clearly has the best line.
...Does road kill even exist in 600AD?
The Sorcerer is a bit of a pain. It absorbs all elements except Fire, which it takes double damage from. It's still usually easier to Ice Water everything else dead and then have Crono and Frog knock it out with physicals. That said, they want to do it quickly, as besides healing all enemies, it can also inflict a decently powerful magic spell that hits the party.
I guess we'd better do something about that!
Soon I remember I have Robo and throw him in to get some Dual Techs.
Oho! Yes, there are even Triple Techs! They all require Crono (obviously), and there's one for each combination of characters. It just so happens the one with Frog and Robo is the easiest to get early, as most of them require later Techniques.
Slurp Cut + Laser Spin. It simply doubles Slurp Cut's damage, with the only real bonus being it hits all enemies in a line from Robo through the target. Situational, but usually not that useful.
On the reverse side, Bubble Snap simply doubles the damage of Robo Tackle.
Finally, Triple Raid. This combines Cyclone, Slurp Cut, and Robo Tackle, and adds 25% more damage to each. This early on, it's going to be your most powerful physical attack available, though due to how it relies on early Techs, it'll fade as the game goes on. But if you like having a party of a frog, a robot, and a Goku, you could do worse.
At the end is this thing.
Is this Flea?
No, this is not Flea. It has a whopping 1HP and when it dies it counters with MP Buster.
Oh yeah, there was a bat following us the whole time. Except that bat was actually a person.
Who is this fiend?
What the...?! Hey, I'm a GUY!
Male...female...what's the difference? Power is beautiful, and I've got the power!
And to be turned into something so hideous! Dreadful! But since you've brought your new friends over to play... Boss Battle 1 
For kicks, Flea gets their own special scrolling space background.
Flea can be a pain. He only has 4120HP, but he has slightly higher defenses than usual, and takes a third less damage from Lightning, Water, and Shadow. Most annoyingly, however, is Flea's propensity to inflict status effects. This will probably be the first time you actually see most of these status effects in a battle, honestly.
Chaos, Blind, Poison, Sleep, Flea's got it all!
Flea even has a spell that inflicts damage to the entire party by making a character attack the others. It's messed up, baby.
But I've got a robot programmed to punch my problems away so it all works out.
Sir Magus...
Slash and Flea are now defeated, so we can progress.
That save point is back, which lets us travel onward.
I was going to try to do the whole thing, but I got tired and this is a pretty good stopping point, so I'm stopping.
We'll finish things up here next time!
