Yeah, I'll say it in invisible font, then just highlight below to see. It's to keep away spoilers for anyone.
Yes, you get the Fierce Deity Mask. It is really neat, and you can do alot of kool things with him. I'll let you find out on your own the rest.
Gyorg was hard. You have to shoot him with an arrow, then dive in the water and bash into him while using your magic blue-shield thingy. I recommend getting some Romani Milk before fighting him again. Also, stock up on faries. If you need info on Romani Milk or any other things, just PM me. I've beaten this game ten times now.
Yeah, so highlight above if you want to know the answers.