Can't find the sun key

[Shanster]

I don't know if this might include possible spoilers for part of the game but I desperately need help on this part and I can't find a walkthrough to explain it all for me.

I am trying to get further into the castle to find Ishtar and Ramires.  I got the moon key and opened up part of the castle but I can't find the sun key or the key to get into the main area.  I am literally running all around the castle and went off into the side area to the right outside of the castle where the dead end is.  Can someone give me some pointers or very obvious hints?  Thanks!

[Mastertrek]

I think that it's in the left-most room in the area with many doors (where you need Moon key for) and you get it automatically after a mini-boss fight. Then you will have to beat another mini-boss to use the switch so you will be able to walk through missing water.