To get the Tail Key for the first dungeon in Link’s Awakening you need to solve the Mysterious Forest. To enter you need the shield which you can get from Tarin in the house you woke up and the sword which you can find at the beach.
Mysterious Forest – Getting the Toadstool
After you entered the forest you need to go inside a cave through a log.
Move the blocks in the second part of the cave and exit it to find an orc and a toadstool. Defeat the orc take the toadstool and return through the cave.
Mysterious Forest – Getting magic powder
Go back to the entrance of the mysterious forest and go up then right and you will leave the mysterious forest. You will see some scary Trees with an entrance, go inside and throw the toadstool in the cauldron. The witch will brew magic powder which lets you get past the raccoon in the mysterious forest.
Mysterious Forest – Getting the Tail Cave Key
Return to the forest and find the raccoon. Use the magic powder on him and it will transform into Tarin! Go up and open the chest to get the Key for the first dungeon in Link’s Awakening: Tail Cave
Mysterious Forest Video Guide
>>Next: Tail Cave Dungeon Guide