i am in the windspear hills temple and have got all [i think]of the pieces of mask. how do i put it together and does it help open the door or is the key u got from the npc used for that? also evry time i enter that corridor i get hit by a fireball apparently from a guardian. where is it?

(Spoiler)
The mask is made as soon as u collect all the pieces. Once finished u put it on and it allows you to see the guardian so that u can fight it. Watch the NPC though, because she turns on u with a group and a pretty tough battle ensues once you get past the guardian and get the treasure.
-Pal