Link has several different Allies in his quest to destroy Ganon.
An listing include these following:
Fairies: These captured by you from the enemies
revive your life by 3 full hears. The ones found in fountains will
renew your whole life.
Merchants: These sell you items such as bombs, keys, blue
rings, arrows, blue candles, etc. Bombs and Keys can be found after
clearing out enemies, most other stuff can be found from the merchants.
Moblins: They are hidden in caves. Not all moblins
are evil, as the ones in caves give out gold.
Old man: Also found in caves, they give out certain items,
powerful swords if you got the correct credentials, useful information,
and even gamble with you.
Old woman: In order to let them help you, you must possess
the letter. They sell the medicine of life, which can be used in labyrinths.
Legend
of Zelda -- Allies 