Zelda: Link's Awakening's Tail Cave dungeon is the first proper trial of the game.
Accessible once you have found the Tail Key in the Mysterious Forest, it introduces a new item - Roc's Feather - which changes how you navigate both the dungeon and the wider world.
If you're looking for more assistance, our Zelda: Link's Awakening walkthrough can help.
How to start the Tail Cave, and get the first three Small Keys and the Map
First, go left and defeat the two enemies by swiping them with your sword and over the edge. Doing so rewards you with a Small Key.
Go left again to the next room with a chest and four torches. These will spit fire until you defeat the enemies within, which also opens the door so you can escape. Clear the room, open the chest for a Compass.
Return to the entrance and go into the room north. Here is a room with several enemies and a switch next to a hole in the ground. Stand on the switch to spawn a chest in the upper right corner, which contains the second Small Key.
Go east to a room full of enemies. Clear these out - the skeletons will require you to swipe them over and over until they are either fall down a pit or are pressed against a wall so you can finally attack them - to make a chest spawn with a Map inside.
You can go north here, but we'd recommend going west and west again into room full of Keese. Once defeated, the door north will open until a large room blocked by a crystal.
Hit that away with your sword, kill the yellow worm enemy on the other side, and do the same again with the one to the east, spawning a chest containing 20 Rupees.
There's another chest to the right with a fireball surrounding it. Wait until it's on the other side and open it up from the south to get another Small Key.
(Before we progress, on the far west side of this large room is a cracked wall, with the map revealing a room on the other side with a chest containing a Secret Seashell location. Without an item - Bombs, which you can purchase from the Mabe Village shop - you cannot access this. Make a mental note and return later!)
How to get the Tail Cave's Stone Beak
Head east to a Locked Door you can open with a Small Key. Inside are two fireballs and a skeleton, plus a door beyond a gap in the floor to the right.
Ignore it for now, and head north to a room with enemies that rotate between different playing card suits on their bellies.
Hit each one so they all match, spawning a chest in the upper right containing a Stone Beak. Use this on the owl statue in this room to reveal a clue about how to defeat spiny enemies.
Return to the large room previously, and head to the north-west corner, where you can open another Locked Door with a Small Key.
This takes you to a long room with another stone owl opposite. You have to make your way around this room in an anti-clockwise fashion, avoiding the fireballs (we recommend sticking to the outside wall to do this) until you reach the stone owl.
With the Stone Beak you collected previously, it'll tell you that, if in doubt, moving blocks will see your path open up.
Take this advice and move the stone block below you south, which will open the door to your left. Head through it.
How to defeat spiny enemies and get Roc's Feather
In this room are two spiny enemies. As the owl statue hinted at earlier, you'll need to use your shield to defeat them. Stand parallel to them, which will see them charge at you, then raise your shield. It'll bounce off, leaving them open to an attack with your sword.
Defeat both then head down the staircase that spawns in the corner.
This leads to a side-scrolling section - just like Super Mario, complete with Goombas! - until you reach the far side. After going up the ladder you'll return to the top-down dungeon again.
Head up, past the circular saw enemies (to avoid getting hit, move just in their way with your shield raised and then back out again, then run past when they are retreating) and open the chest.
Inside is Roc's Feather, and item you can equip to leap over holes in the ground and other obstacles. Equip it and you'll be able to grab the floating heart piece on the corridor just south of here.
Our Zelda: Link's Awakening walkthrough and guide can help you with the critical path, including the Eagle's Tower and Turtle Rock dungeons. There's plenty to be done on the side, too - including Zelda Link's Awakening Heart Pieces, Zelda Secret Seashells and the Zelda Link's Awakening trading sequence. Finally, there's also the new Zelda Chamber Dungeons feature to unlock and complete.
How to get the Tail Cave Nightmare Key and beat the Tail Cave mini-boss
Head back through the dungeon the way you came until that large room where you found the Small Key and the red Rupee. Head north-east in this room, and using Roc's Feather, you can leap over the gap and use a Small Key to unlock the way up the staircase. After that, go left and open a chest to get the Nightmare Key.
Head back down and through the south-east door, to the room south of where you got the Stone Beak. You can now leap over the gap to the right and go through the door, where you'll encounter a mini-boss.
This purple mini-boss will roll a spiked column across the floor towards you. Every time it does so, leap over it with Roc's Feather, then attack the boss with your sword.
Repeat this process until it is downed. It's a simple encounter, but it's easy to accidentally run into the boss after you leap over the column; so we recommend staying at the bottom of the screen when leaping, then moving up into the boss when you're sure it won't collide into you.
Once done, a Fairy will appear (which can heal you, or captured with a Bottle if you already have one in your possession) and a portal will open up in the centre of the room. Standing in this will teleport you to the entrance of the dungeon, and from there, back again to this location.
Head north to a room with the Nightmare door, leading you to the boss. If you haven't already, grab the Nightmare Key - it's found in the largest room in the dungeon, and requires you to leap over the gap in the north-east corner using Roc's Feather to find the chest.
There's also a staircase here, leading to a side-scrolling section and several hanging skeletons. There's nothing to do in this room - it's actually where you'll appear if you get knocked off the ledge in the upcoming boss room.
When ready, head through the Nightmare door to take on the dungeon's boss, Moldorm.