Right outside you can quickly unlock some better music and a 3 hit health system! Not one you want to miss.
Follow the path until you find the chest with textures by the Dimensional stone. Now that you're in 3D, you can very easily step over the stone. Where they always this small?
Head back through the early game levels until you find the other Dimensional stone and move past it to continue.
Keep following the path down, if you find the HD textures and get pulled over by Sevan, you're going to right way.
In fact, just after Sevan pulls you over is the end of the map. After unlocking the 3D Overworld, make your way into the Mines.
Open the chest to unlock three paths into the mines, but you can only go up right now.
Unlock a chest up ahead to make 2 pressure plates appear. Step on both of them to make another chest accessible.
A chest blocking the way forward forces you to unlock an annoying new enemy, the Red Wizard. He appears, shoots a fireball in a line, and then disappears. More of a pain then it sounds.
Step into the room past the locked door to unlock... Trap rooms, goodie. Kill all the enemies to get out, but also to unlock the key you needed.
Through the locked door is another forced enemy unlock, the Skeleton. Very similar to the statues from early game, you can only hit their sides. Unfortunately these has more AI which makes them a pain.
Press the nearby pressure plate so that something happens and then make your way through the maze.
Inside the maze you'll find another key for the locked door North-West of the maze.
You'll unlock pushable blocks now, I'm pretty sure you shouldn't need me to tell you to push it into the pressure pad you can't reach normally to open the door.
After a Skeleton Trap room, you unlock an endless pit to push a strangely invincible octo into.
After a pointless decision, you'll (unlock and then) come across some whirlwinds. Time your way across the ledge of prepare to get blown into those pits you unlocked.
You'll then get a light puzzle. Step on all the tiles to light them up without doubling up or stepping off.
To get the key needed for the locked door, you need to traverse through a room with spikes and whirlwinds.
Through the locked door is a save point and a chest that unlocks lava (and the way forward).
The next room is filled with an invisible maze. Some tiles are safe, but some are trap doors that open up to lava underneath when you're near. Just move slowly and feel your way through and you should be fine.
After some simple fireball puzzles you'll get locked into a big trap room. This one is filled with stuff and is kinda hard. Remember to break pots for health!
A chest on the right contains the Boss key which transforms one of the original paths into a Boss door. Conveniently, the path to the left loops back to the first room where the Boss door is. How nice!
What else to be found through a Boss door than a Boss! It's a shadow clone of you, or something... It's never really explained.
Shadow Nien attacks by shooting 3 fireballs at you and doing a charge dash. You also can't attack him normally.
Trick him to charge into a wall, he'll get stunned and be open for your attacks.
After some hits, he starts summoning Black Bats, but you still kill him the same. The bats are mainly there so you can kill them for health.
Once you squash Shadow Nien, you'll unlock a sweet new sword! Now kids, who can name what game this sword is from?
Out of the cave you unlock 3D overworld fights, but other than that, push onwards to Sevan's town!