Deltarune Chapter 5 — Secret Boss Full Guide

⚠️ Warning: Spoilers ahead for Deltarune Chapter 5!1 Deltarune, Toby Fox’s episodic follow-up to Undertale, has a tradition tucked away in every chapter: a hidden, optional boss far nastier than anything the main story asks of you. They’re not required and they’re easy to miss entirely, yet they’re some of the toughest, strangest, and most lovingly made fights in the whole game.

Who Is the Deltarune Chapter 5 Secret Boss?

1 Chapter 5’s secret boss is Pink, better known as Mad Mew Mew — the possessed Mew Mew Kissy Cutie doll turned Darkner, here serving as the chapter’s Shadow Crystal boss (and possessed by a ghost Lightner during the fight itself). She’s locked away behind a pink door.

Step 1 — Collect 10 Pink Coins

9 To find the secret boss in Deltarune Chapter 5, collect 10 Pink Coins, buy the Mystery Key from the pink shop by the Cliffs, then use that key on the large pink door near the late-game castle route. 7 They drop from platformer-mode ear-bubbles and pink chests scattered across the chapter. There are way more than 10 total, so you can relax once you unlock the teleport door. One coin sits right in front of the boss door — grab it if you’re short.

The game doesn’t track your count in the inventory — count manually. 9 You do not need to find every Pink Coin the first time you pass through an area. In fact, some coins and paths make more sense after you unlock more movement, activate teleport doors, or understand how the chapter’s 2D sections work.

Step 2 — Buy the Mystery Key

9 Play normally, check optional paths as you go, then do a focused Pink Coin and Mystery Key sweep before committing to the end of the chapter. 9 Once the Mystery Key is in your inventory, stop searching around the shop. The key is bought there, but it is used much later. The pink door is near the late-game castle route around Green’s Shop, not near the Cliffs shop.

Step 3 — Find and Open the Pink Door

10 The start of this secret boss comes very late in the chapter. The side route towards the boss comes after Green’s pop-up shop during the final ascent to the top of Flower Castle. If you have the warp doors unlocked, start at Green’s Shop and head to the highest part of the platforming gauntlet found to the right. 

Once Ralsei casts a spell he’s only alluded to during a cutscene, hop up and take a left rather than continuing right. From here, bounce on the blue rose launchers to avoid falling into the brambles. Once you’re halfway across you’ll be able to drop down via some platforms. 9 The safest clue is Ralsei warning that the fountain is not that way.

If you see that warning after buying the key, keep going. 10 At the bottom of the fall you’ll find a strange monster wandering towards a giant pinwheel. Use the ACT menu to start the pinwheel, kicking up wind and starting a slow descent through brambles and gunfire.

Step 4 — Prepare for the Fight

9 Before opening the pink door, save and stock up on healing items. The door leads to optional boss content, so do not walk in with a weak inventory just because you finally found the route. 10 Generally, focus on stocking your inventory with powerful healing items and any ReviveMints you may still have.

If you’re aiming for Secret Bosses, you’ve probably already used quite a few of them. Luckily, Ralsei’s Revive Song spell does wonders to keep the party on their feet. Green’s GreenTea heals a very handy 180 HP per use, so stock up if you’ve got open slots. 10 Focus on maximizing the TP you can make with Armor like the Ribbons that grant you extra Graze Area.

Pacifist vs. Violent Route

8 You can defeat the secret boss using the Pacifist method by maximizing your Tension Points (TP) through grazing. This allows you to cast specialized ACT spells to spare the boss, which rewards you with a highly defensive armor piece. 8 The Pacifist and Violent routes yield completely different rewards, offering either defensive armor or an offensive weapon.

Rewards for Defeating the Secret Boss

1 Beating her yields the chapter’s Shadow Crystal. 7 Defeating it also unlocks a special item and a journal entry. It’s on the full completion checklist for Chapter 5.

All Deltarune Secret Bosses — Quick Recap

1 The secret boss tradition spans every chapter — Chapter 1 features Jevil, Chapter 2 features Spamton NEO, Chapter 3 features The Roaring Knight, Chapter 4 features The Hammer of Justice, and Chapter 5 features Mad Mew Mew (Pink).

Tips for the Secret Boss Fight

• 10 Don’t panic, focus on keeping the party healthy, and don’t forget to use Ralsei and Susie’s unique ACTs.

• 7 The boss has high damage output and unique attack patterns. Equip your best defense, stock healing items, and learn the telegraphs. Patience and pattern recognition beat aggression here.

• 1 Like every Deltarune secret boss, expect a sharp difficulty spike and dense bullet patterns, so save and stock up on healing first.

• 9 You are ready for a fight that may take a few attempts. Do not worry if you lose once while learning.

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