World of Final Fantasy/Chapter 3: Old Acquaintances

Cornelia Region
There's only one way to go in this area, so head down the right fork and enter the cave.

The Nether Nebula
Finally, you arrive in the first dungeon. Most dungeons in this game are very straightforward, with the occasional fork. Just follow the path down the dungeon until you reach the first Puzzle Platform. These are switches which requires you to stack mirages on top of them to fulfill certain conditions. This one, in particular, requires at least 50 earth resistance, and at least 5 weight. A Copper Gnome alone can fill this one. A bridge across the gap will appear, and you will see another switch on the other side. This switch requires 75 earth resistance and 5 weight. You can use a Copper Gnome and Mini Golem for this. The fourth area of the dungeon has no encounters, a save crystal, and a fork to the east which currently is inaccessible.

At the end of the fourth area you will see a save crystal. Approach it to enter a cutscene where Tama will reveal a red cage further up, known as a Threshold. These are typically created by powerful mirages residing within, and her powers of saving you won't work inside. In other words, if you die in there, game over. Save, then approach it for another cutscene where you will meet Ramuh, Shiva, and Ifrit. They appear to know you, even if you do not know them. They will reveal to you that you used to command all three of them, but are currently too weak to even control one. They will offer to test you, and you will get to choose which of them to fight. Which one you fight determines which "starter" Mirage they will give you. Shiva will give you Bablizz, Ifrit will give you Fritt, and Ramuh will give you Zapt. All three are available when you revisit this dungeon at a higher level, albeit at painfully low encounter rates.

Nine Wood Hills
Nothing super interesting happens here. Head back to your room and leave it to unlock a quick-travel option while in Nine Wood Hills before returning to the gate and heading to Cornelia.

The Nether Nebula Secret Area
Once you are around level 20, you can return to the fourth area with Mirages that know Flutter and Smash, in order to access this dungeon's Secret Area. Mirages here will be at a higher level, and will be the only location of the other two "starter" Mirages you didn't pick for a very long time. Don't worry, if you enter this area too early, the Mirages here will make sure you know. They will hit you for half your health, and you will only return the favor by poking them.