Zelda 1 - Walkthrough of Dungeon 9 of Quest 1: Death Mountain (Zelda I NES mini)
Map of the labyrinth "Death Mountain": Dungeon 9 of Quest 1 from Zelda I (The Legend Of Zelda NES mini)

I haven't listed all the keys below the map but normally you should have found the master key in level 8.

Go up twice and blast a hole to the left, then kill the caterpillars to take the passage (1). Go right and go down twice through holes (2). Kill the enemies to get the compass. Go up twice and go right. You are in G2 in front of Patra who "guards" a locked door — I recommend killing it (3).

If you want the red ring, go down and blast a hole to the right (1) (killing Patra gives you the map (2)), then two holes upward. Kill the Wizzrobes, take the red ring (3) and come back to G2.

Go up, blast a hole to the left and kill all enemies to push the left stone, making a passage appear (1). Go left twice and kill Patra to take the underground passage. Blast a hole upward, kill all enemies and push the middle stone to find the silver arrow. Go back down, kill all enemies and take the passage. Go up three times killing enemies if needed to open the doors, then blast a hole to the left. Kill the monsters and push the left stone then go down the staircase. Kill Patra, the door opens — the hour of the final battle has come.

The boss is Ganon. As soon as you enter the room, Ganon disappears. Swing randomly in all directions to hit him. After 4 hits (he appears when struck), Ganon turns brown (3). You must then pierce him with a silver arrow to reduce him to a pile of dust and claim his Triforce.

Dungeon map in Flash
Dungeon map in PNG

Small Key : H5 - B7
Dungeon Map : D6
Compass : F4
Red Ring : H1
Silver Arrow : A2

You have completed the First Quest.. Here is a save file (an 8 KB .sav file).

You can now start the second quest, which, fair warning, will be much harder. Here is a save file (an 8 KB ".sav") that lets you start in the second quest (if it does not work, just name your character Zelda).