Ho ho ho... With this, the
seal of the seven sages is
at last broken.
It is now only a matter of time
before evil power covers this
land completely...
After all, the legendary Hero
cannot defeat us, the tribe of
evil, when we are armed with
the Power of Gold.
Ho ho ho... Now, I must go!
So it's tribe of evil, but it's not impossible that the same word was translated as 'tirbe of darkness' in FSA. However, if I remember they use capital letters to refer to it in FSA, so I expect it was a more direct translation, a proper official name for something.
魔族 means something like "magical race", which is something like "demon".
This word is used a few times in ALttP, once by Sahasrahla when referring to the Knights of Hyrule battling Ganon's army of 'demons'. It's then used by Agahnim and is translated as tribe of evil. Sahasrahla later uses it to say that the 'demons' run rampant in the Golden Land meaning it's a 'World of Darkness'.
All the Maidens use it when they talk about the 'clutches of the evil monsters'.
I wonder how it's said in Japanese. Sounds very much like 'Mazoku' from the anime Slayers, which is translated as 'Monster' on some translations of the books and anime, which causes no end of confusion. I doubt it's as specific as in that series though, there doesn't appear to be much noticable difference between 'demons' and monsters.