I had asked about being stuck in the Crystal Tower not being able to find this Xande guy.
Anyway, I finally found out that you have to go into the door on the left wing of the tower to the north. When you get to this special doorway, you actually have a cutscene where you use the 'crystal's light' to open that passageway.
Then you get into this passageway area and there's this treasure chest. When you walk downward from that treasure chest, there's actually an opening in the right side of the wall and you can walk that way. You can figure everything easily from there. Good luck!
[Note:] You have to be well above level 50.. Maybe level 60 or 70 to beat the game smoothly.
And once you beat Xande which in my opinion, was fairly easy at level 50, you'll have to keep continuing foward and won't be able to go back and save or anything. So it's not really a good place to level up unless you have a shitload of hi-potions, elixirs, and other supplies.
I tried this whole deal around level 52 and i got my ass served. It sucked. And then since I couldn't save, I had to do everything... levelling up, gathering items from chests and such all over AGAIN.
So, prepare before you go and fight Xande, even though he's easy to beat. Good luck.