where do i find this?

Kill a silver dragon. There's one in the Underdark (chapter five). But if you ask me it's really not worth all the work, the armour you get off that bloke for doing it stinks compared to most every other piece in the game.

are there only 3 dragons in the game?

AS long as your only counting major dragons (Not Pseudo etc), then their are only 4: 1 Silver, 1 Red and 2 Black.

Im wrong,their are 5 dragons in the game, I just remembered another, that makes 1 silver, 1 red and 3 black. This time im sure im right?

Hmmm...

There´s the shadow dragon, the red dragon, the silver dragon, the black dragon, and the last one, I think, is the golden dragon, but you don´t fight him unless you´re evil (or want to be). Same would go for the silver one, I believe.

wheres the gold dragon?
temple ruins, windspear dungeon, underdark, suldenessalar
any others?

<font color="gold">Hmm, cant say I've heard of any Gold Dragon. I'm sure that it doesnt exist.
I think you remeber wrong, Hermit, as there are no Gold Dragons in SoA. ;) </font>

i seriously doubt that there is a gold dragon in soa. ive played through the game quite a few times and never seen a place where there could be a gold dragon. if there is, please tell me where.

Actually, the gold dragon was either green or black. It was too gloomy to tell.
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He's in Hell and you don't have to fight him. I don't remember if he dropped anything worthy.