How to Beat the Shadow Mantle Secret Boss in Deltarune

Deltarune's Chapter 3 introduces one of its most elusive challenges yet—the Shadow Mantle, a hidden mini-boss that requires solving intricate puzzles and mastering multiple minigames. This guide provides a step-by-step walkthrough to unlock the encounter, strategies to defeat the boss, and details on the powerful Shadow Mantle Armor reward.

Deltarune: How to Beat the Shadow Mantle Secret Boss

Prerequisites:

• Complete Tenna’s Board challenges with an S Rank (twice).
• Successfully finish three unique console minigames in the S Rank Door area.
• Obtain the Shelter Key in the second minigame.

Step 1: Earn S Rank on Tenna’s First Board

• Objective: Collect all four keys and perform well in the cooking minigame.
• After achieving S Rank, enter the S Rank Door.
• Go left to find an NPC who grants access to the backstage area.
• Locate the first console minigame.

First Minigame Walkthrough:

Find the Controller:

• When prompted with "No Controller," search the right side of the room to pick it up.

Level Up to 3:

• Defeat enemies until you reach Level 3.

Chop Cacti & Trees:

• Go right, destroy cacti to reveal a hidden area.
• Return to the forest, chop trees until a red treasure chest appears.
• Claim the Ice Key.

Step 2: Earn S Rank on Tenna’s Second Board

• Objective: Collect all four photos, eat moss, and excel in the concert minigame.
• Re-enter the S Rank Door to play the second console minigame.

Second Minigame Walkthrough:

Get the Sword Early:

• Enter through a hole in the wall to grab a sword.

Reach Level 2 & Sail Upstream:

• Head right, use a raft to travel up the river.

Unlock the Blue Door:

• Use the Ice Key to enter a dungeon.

Obtain the White Cloak:

• Clear enemies, cut down two trees, and proceed left to find the White Cloak (grants freezing attacks).

Navigate the Maze:

• Follow paths where the White Cloak accompanies you—if it stays behind, turn back.

Claim the Shelter Key:

• Exit the maze to find the Shelter Key, ending the minigame.

Step 3: Play the Final Minigame & Trigger the Boss Fight

• Return to the Green Room after Tenna and staff leave.
• Re-enter the S Rank Door for the third minigame (now with Susie and Ralsei).
• No enemies? Stab Susie and Ralsei to level up.
• Break a barrier, take the right alley, and descend a manhole.
• Meet Toriel, who guides you to the Shelter.
• Use the Shelter Key to unlock the door and encounter the Shadow Mantle.

How to Defeat the Shadow Mantle (4-Phase Boss Fight)

Attack Patterns & Counters

Phase Progression:

• Each phase increases attack speed and intensity.
• Final phase: Enhanced versions of all attacks.
• Key Tip: Stick to the same evasion strategies—don’t panic!

Reward: Shadow Mantle Armor

• After winning, open the treasure chest (must exit/re-enter with real Kris).
• The Shadow Mantle Armor provides bonus stats and is essential for fighting the Roaring Knight (another secret boss).

Pro Tips for Success

✅ Prioritize dodging over attacking in later phases.
✅ Use healing items dropped by enemies during the Friend Attack.
✅ Equip the Shadow Mantle on your tankiest character for survivability.

Final Thoughts

The Shadow Mantle is a true test of patience and skill, but the reward justifies the effort. Follow this guide meticulously, and you’ll conquer Deltarune’s toughest hidden challenge!

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