Graveyard Key

Oracle of Ages
The Graveyard Key is found in Oracle of Ages, in a secret cave in the southern part of Yoll Graveyard. It is needed to open a gate in the northern part of the graveyard, in order to then access the eastern part and reach the Spirit's Grave.

The Minish Cap
A Graveyard Key also appears in The Minish Cap, where Dampé the gravekeeper gives it to Link. As Link steps out of Dampé's house a crow steals it. By killing the bird in this same area, he will get it back and then be able to enter the graveyard.