Total Conversion: Ys III vs. Ys: The Oath in Felghana
Here's the beginning of the Elderm mountain range.
And some scenery from the mountain range.
These are the caves. They're much larger and more intricate in OiF. You also need to obtain snow shoes so you don't slide all over the ice in certain areas. It's here that you also get the Earth bracelet, which lets you demolish brick walls.
Here's the hut of Berhardt, Dogi's master. He has no real role in Ys III beyond some exposition, but he does a bit more in OiF, eventually.
The first boss fight on the mountains. In Ys III it is against a single harpy. In OiF it's against a trio of harpies, who are called to the field to Dularn. Just note that it's easy to trip up here - the game lets you go to the mountain ranges, and even tells you as such, but this event will not trigger until you've talked to specific people back in Redmont.
And the boss, another dragon. It's awfully stationary, compared to some of the other dragons you fight. In OiF, it will also snatch you and fling you high into the sky, forcing you to dodge various rock outcropping on your descent back to earth.
The commotion causes the entrance to collapse. In Ys III, Chester gets caved in with Adol, and he uses their time trapped together to explain the plot, which was a pretty cool plot device. In both cases, the wreck is cleared by Dogi the Wall-Crusher. Chester simply takes off in Ys III, but in OiF, he meets Dogi and Adol outside the cave, which is instead where he reveals his intentions. He also stabs Dogi, steals the statues and sets off.
The town is invaded. In Ys III, nearly all of the townspeople are kidnapped and taken to Valestein Castle. In OiF, they're still there, but they're shaken up about the attack. At this point the town theme changes to the "sad" version. And so, Adol heads off to Valestein Castle to stop Chester and his plot for revenge. In Ys III Elena meets you at the entrance and gives you a pep talk. In OiF she's already run ahead (and gotten herself captured) so instead one of the maids is outside asking you to look for survivors. Also note that in Ys III you see the castle in the background, and technically you're going through a few underground sewer screens to reach it. In OiF you just waltz through the front door. There are sewer sections, but they're in the latter half of the area.
Valestein Castle is full of traps - Ys III has spikes and mechanical statues that smash you with their axes. OiF has the spikes too, along with boulders, swinging rocks and other fun bits to dodge. After the first few screens, it also opens up a bit and allows you to explore each of the two spires separately. The overall goal is to collect the three broken parts of the organ to open up a secret passage underground.
This quick moving assassin is the boss of one of the spires in OiF. There are also spikes that come out of the floor. As a result the fight is much different.
Exclusively in OiF, here's where you meet McGuire's family, who serves no real function beyond humanizing one of the villains. You also get one of the items for the organ here.
This wolf is the boss of the other spire. Again, Ys III is totally linear, so you fight these one after another, basically, with some brief screens breaking them up.
And here's the chapel. This is opened automatically with the help of one of the priests in Ys III - in OiF you need the organ pieces, as mentioned above.
This leads to the sewer section of the castle.
In Ys III, you need to get the jail key by beating this knight. These statues have been throughout the game and hinder your progress if you don't have a certain item, but this one comes to life. It was turned into some kind of mechanized cannon thing with machine guns, missiles and other crazy armaments in OiF.
Here's the people in the jail cell. In OiF, Elena is amongst them. Note that also here is Bob/Roy, who isn't quite dead!
Right, on to the clock tower. This is the only stage in Ys III that has any extensive platforming elements, which wasn't the best idea, because the jumping and such is not very well implemented. This area is quite linear in OiF too and mostly serves as a platforming challenge, although the exit door is in each room is locked, requiring that you find a statue in some other part of the area.
Here's the bridge that leads to the (not quite final) encounter.
In OiF, there's another fight with Chester before you reach the room.
The bishop reveals his true form as Garland (Merland in the Genesis version), who has been manipulating McGuire (and Chester) the whole time. He's a standard boss fight in Ys III - in OiF he's invincible, because his barrier can only be shattered by the final sword, which Chester will soon give you.
In Ys III, Elena is dramatically captured by having the bridge crumble beneath her and then be whisked away by Galbalan as a hostage. In OiF, it's originally Chester who's captured, because he's of the proper bloodline to resurrect Demanicus, but Elena offers herself in his place, so she's kidnapped instead.
In Ys III, when Adol leaves the castle, he ponders his competance as a hero. He's a much more likable hero when he doesn't say a word or or worry about internal conflicts.