Graveyard Key

The Graveyard Key is found 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 open the eastern part and reach the Spirit's Grave.

It also appears in The Minish Cap. Dampe gives it to Link the grave keeper. As you step out of his house a crow steels it. By killing the bird in this same area, you will get it back and then be able to enter the graveyard.