Deltarune Chapter 5: Get the Petal Feather to Power the Mysterious Structure

Inside the Dark World of Deltarune Chapter 5, the vines that Asgore and Flowery sit on top of cannot be climbed at first, and the Mysterious Structures scattered around the area stay inactive when you interact with them. Both problems share one solution. You need the Petal Feather, a power earned by defeating the boss Aqua, which lets you switch into a 2D platforming mode and bring those structures to life.

Quick answer: Reach the watering can past the diner, use it to reveal the path to a rock structure near a torii gate, beat Aqua through the opening, and collect the Petal Feather. Return to the Mysterious Structure beside the “Exit” sign, interact with it, then climb the vines, which are now leaf platforms.

Why the vines and Mysterious Structures are locked

When Kris, Susie, and Ralsei first try the vines, they climb part way before hitting a gap they cannot cross, so they drop back down. The path to the right that continues the story is also sealed until you find the source of power. This is the first moment the game forces you to use the Mysterious Structure ability, and you cannot progress forward without it. Trying to leave back to the Light World does not work either, since Susie stops you.

Reach the watering can past the diner

From the “Exit” sign, head left instead of going for the Light World route. Follow the path down and you will arrive back at the diner where Asgore and Flowery were having a milkshake. You can spend Dark Dollars on armor and healing items here before moving on.

The door that leads to Aqua in Deltarune

Take the door in the middle of the diner and follow the path upward into the dark room. When the path splits into two directions, take the path on the right and keep moving up.

Take the first path going up when you reach one. This leads you to a watering can resting on top of a pink pedestal. Pick it up.

The watering can reveals grassy walking paths in the dark room that are not visible otherwise. Press A/X to use it. Reveal as many paths as you can while you work toward the exit.

Find Aqua and collect the Petal Feather

Head left from where you found the watering can and keep working across the room with the watering can active. Look for a rock structure that sits near one of the torii gates. It appears just northwest of the first chest in this area, which holds a Green Tea.

Go through the opening in the rock structure. You will lose the watering can here, so collect any nearby chests before passing through if you want them. Inside, you encounter the boss Aqua.

Defeat Aqua. After the fight, follow the single linear path forward and climb the steps at the end. The Petal Feather waits there for you to pick up.

The Petal Feather changes how certain sections play. With it, you can switch into a 2D platforming mode where Kris can jump and attack. More importantly, it is the exact power the Mysterious Structures need.

Activate the Mysterious Structure and climb the vines

After returning to the standard third-dimension view, make your way back to the “Exit” sign and head right. You will find a Mysterious Structure there. This is the same path that was blocked before you had the feather.

Interact with the structure to activate it. This changes the terrain in the connected room, swapping the unclimbable vines for leaves that act as platforms.

Go to the room on your left, back to the vines where Asgore and Flowery sat at the top. Use your jumps to scale the leaves all the way up and continue chasing Flowery.

How to confirm it worked

You will know the power is active when the Mysterious Structure responds to your interaction instead of staying inert, and when the previously blocked vines change into leaf platforms you can stand on. If the vines still show a gap you cannot cross, you have not interacted with the activated structure yet. Step on the structure beside the “Exit” sign first, then return to the vine room. The structure must be powered for the leaves to appear.

Once you reach the top of the vines, the main path forward opens again and the chapter continues. From here you can pick up any collectibles you skipped, including the Red Ribbon hidden in the heart-shaped grass near the stone wall exit.