You follow the echo to Eternal Forest, and solve the ancient riddle there. It leads you to the Stilled Ancient Ruins.

Reach the First Waypoint

Go east, then north up the floating trees. You can go west if you want to go through a desert landscape, or go east if you want to go through a watery landscape. Both paths lead to the same area. Check on the waypoint when you get to the snowy island.

Reach the Second Waypoint

Go west from the waypoint and make your way north on the ice, but beware of the Dark Freezards. Go northeast from the Freezard area to reach a wetland area.

In the wetland area, beware of dark Buzz Blobs and a dark Giant Goponga Flower. Make your way south past where the flower was, then go east to a volcano area. Create a flying echo such as a Keese, and float up in the air vent. Continue floating up on the vents to reach the ledge to the north.

Defeat the Dark Fire Lizalfos and the Dark Zirro, then use echoes to go up to the air vent to the west. Use a flying monster echo to float west to the next air vent, and from there to the waypoint to the west.

Then go north to an area of randomly assembled pieces of terrain. There will be a cutscene.

Echo Zelda

You must battle Echo Zelda. Defeat the dark echoes that she creates (Darknuts, Ice Octos, Buzz Blobs, Freeze Slugs, etc.) and collect the energy that they drop. Hit Echo Zelda repeatedly, and eventually she falls to the ground. Hit her repeatedly. After this, she will use a wider variety of echoes (Tweelus, Fire Lizalfos, Drippitune, Darknut Lv. 2, etc).

After the battle, shoot the crystal that Link is trapped in. There will be a cutscene. This completes the quest "Rescuing the Hero Link".

Talk to Link to return his weapons to him. If you're ready, say Yes when Tri asks. There will be a cutscene. Go north when you're ready.

Null's Body

Follow Link through the area and help fight the dark monsters that attack. When the Dark Lynel attacks, try to create echoes that have a strong shield, such as Sword Moblins.

In the next room, you're separated. Go through the northeast door.

Hold Y to create an echo on the other side of the bars, then use the right stick to look to the east side of the room and hold ZL to target the orb so that your echo will hit it. Then go through the north door.

Create echoes to defeat the monsters on your side, and you can create echoes on the other side of the bars to help Link as well. Then go north.

Go down the stairs.

Bind to the platform above you and hold R to let it take you to the other side, then press ZR to let go of it.

Let the bottom platform take you to the left, then create a cloud on the left side and jump up and down on it while you wait for the upper platform to come over. Hold ZL to target the upper platform, then when it reaches its lowest point, press X and hold R to let it take you up to the ledge on the left. Go through the opening on the left.

Use an echo to destroy the Gustmasters in this area, then create clouds or other echoes to reach the next parts of the room. Go up the ladder at the end.

Go through the east door.

Create an echo through the bars for Link to reach the upper-right corner of the room. You can bind to it with X to move it as needed. Then go through the north door. Continue going north. Jump down into the hole at the end. There will be a cutscene. Then the final battle will begin.