Deltarune: Where to Use the Mystery Key

2 hours ago 2

Published Jun 24, 2026, 8:11 PM EDT

Laurence Wall is a Contributor at DualShockers who has been writing professionally since 2022 and covering games since 2023. He primarily writes guides and lists, with a focus on indie games, RPGs, ARPGs, Soulslikes, MMOs, card games, boss fights, and detailed tutorials.

Before joining DualShockers, Laurence worked as a game reviewer for Movies, Games and Tech. He also co-founded and served as a contributor liaison for a university creative writing magazine, where he was one of the publication’s principal contributors. Laurence holds a B.A. in English Literature and Creative Writing from Royal Holloway, University of London.

Chapter 5 of Deltarune has finally arrived, and with it, we journey inside Asgore’s Flower Shop to a brand new Dark World in search of more answers.

If you’ve played through every piece of the previous Deltarune chapters, you’ll be more than aware of the fact that secret bosses exist, and getting to them is often a bit of a chore.

Within the Flower World, there exist a bunch of Pink Coins, earned by solving little puzzles and finding secret areas within the level. Once you’ve earned 10 of these, from a total of 19, you can purchase a special mystery key and unlock the entrance to a secret boss! Let’s see where to get this key, and how we can find the mysterious Pink door.

The pink door can only be found just before the final boss of the chapter, so make sure you get as far as possible before attempting this.

Purchasing the Key

Once you’ve got your hands on ten of those elusive pink coins, you need to head back to the Shop in the Cliffs area. Simply head to any fast-travel door and select the shop choice via the Cliffs.

Once you’re there, simply head up the steps, and you’ll arrive at the shop. The Mystery Key is the 4th option. Grab the key, and then head on back to Green’s Shop.

Finding the Pink Door

Once you’re in Green’s Shop, head to the right and then jump all the way up to the top of the area. Here, you’ll need to go left.

You’ll find yourself in a long room with some of the bouncy wines swinging back and forth. You need to run, jump, and swing your sword to bounce on the flower. If you fall, you’ll take a small amount of damage and return to the beginning of the section. Cross the flowers, being careful to avoid the floating knives and head down when you see the Winged-Deltarune symbol.

There is an optional platforming section if you keep going left. Here you can find another pink coin.

Here you’ll find a pinwheel. Use the action key, and spin the pinwheel around to remove the platform below you. You’ll need to slash as you're falling to break the blue flowers and manoeuvre through the gap that was created.

In addition, you’ll also find guns that shoot ring attacks. Just focus on your Soul, as this is the only part of you that can be damaged. The easiest way to avoid the rings is to move horizontally as you fall. Either way, you shouldn’t take too much damage if you’re hit a few times. Keep falling, and eventually you’ll exit this vertical section.

In this new room, you’ll spot a large door, as well as a switch to swap perspectives. Return to your normal form and use the key on the door. Here you’ll find the new secret boss of the Chapter. I won’t spoil that here, though! Make sure you buy plenty of Green Tea, and you can return here through any fast-travel door when you’re ready.