-After the scene with Pyros, you should return to the Obsidian fortress and
kill the Master. Take the Tongue of Flame from him.

Now you need to visit Mythran and learn some spells from him. You want to
get the "Ethereal Travel" spell from him for 250 coins. To get money, I
slept in the Jeweler's bed for an hour and she was gone when I woke up. I
robbed her blind, and then went back to sleep again. She was back upon waking
so I sold her all her gems and had enough money. I'm too kind...

Once you cast Ethereal travel you'll need to defeat each element. Use each
symbol on each respective Titan. Here are some tips to ease getting to them:

Earth: Use "Endure Heat" to get past the lava. I don't get the rocks part.
Water: Just keep hopping!
Fire: You'll need a bunch of white balls to drop on the glowing squares.
Air: Ignore all treasure! Just KEEP hopping...

Once you have beat them all and have 4 glowing objects, place them on the
Pentacle in this order:
Mesostel Pa - Heart of Earth
Perivolcan Pa - Tear of Seas
Perivolcan Ze - Tongue of Flame
Mesostel Ze - Breath of Wind
Aphelion - Obelisk tip

Then double-click on the Tip, and then click on yourself. This should then
open the Black Gate if you have them in the right order.