I'm confused. >_> Need some help.

Now, the reason I am confused is because currently, I am further in the game than my half-way run, as I have just (SPOILER)killed Doga and Unei. However, in my half-run, I have all four crystals. In my current run, I do not. Sadly, the Walk-Throughs on Gamefaqs don't mention when you get crystals, so it's hard to tell when you get them with those guides. Now, based on this, it seems as though the fourth crystal is optional, or you can just get it at various points in the game.

So, really, I just want to know where the fourth crystal is. >_>

The fourth crystal is in the Ancient's Maze, right before the Crystal Tower. As soon as you enter the Maze, go straight into the room in front of you. You'll fight a boss named (SPOILER)Titan

EDIT - Also, the maze is located on the Northeast corner of the map

Oh, I see. Thank you.