Mortal Shell II Zmey the Unbidden: Final Boss Phase Breakdown, Endless Core Prep, and Flame Dodging

Zmey, the Unbidden is the dragon at the center of everything — the last combat gate before the ending. It is a fire-and-distance fight built around three readable mechanics. With the Endless Core prepped and a mobility Shell, it is broadly considered easier than Malborn Offspring. Skip the prep and it becomes a furnace.

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Table of Contents

1. Preparation: Endless Core, Flame Mitigation, and Summons
2. Core Walkthrough: Reaching Zmey and Surviving Both Phases
3. Important Notes: Side-Steps, the Flare Window, and the Red Icon
4. Rewards, the Gloom Doorway Trap, and the NG+ Handoff

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Preparation: Endless Core, Flame Mitigation, and Summons

• Endless Core first. The Hidden Nave Beacon becomes accessible after you clear the corrupted tendrils in the Unfound Path. Inside, a torch reveals a fog-hidden route to a stone altar holding the Endless Core. Install it at the Tarforge in Marrow Keep to remove the +16 weapon cap and upgrade past it. The exact post-cap level ceiling is not stated; sources confirm “beyond +16” only.
• Flame mitigation. The Seedbearer’s Scripture, found in Night Mode, mitigates fire damage on its active and passive effects. Pair it with the Burnt Effigy Tarstone (or item) for burn resistance — Zmey and Magdalena both pay it back.
• Summons cost Glimpse. Genessa and Tiel can be summoned just in front of the updraft to the arena, each for one Glimpse. Bank Glimpse so the aggro split is available; it is permanent for that arena.
• Seals for Riposte. Untarnished Seal and Infinite Seal build Break Damage through parries, setting up a Riposte burst. The Slayer Seal also grants Break Damage via sidearms but disables achievements.
• Rest at the Beacon. Cleanse and rest at Hidden Nave before the fight. Walking in with half resources wastes the attempt.

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Core Walkthrough: Reaching Zmey and Surviving Both Phases

Location: Past the Hidden Nave Beacon in the Unfound Path. Take the updraft behind the Beacon into the final arena. Access to the Unfound Path itself requires collecting the Ova (reported as 168) at the Gloom Siphon in Marrow Keep.

Phase 1 — leap, line, and flare. Zmey leaps away and follows with a Blade Slam that sends Cosmic Flames in a straight line. Dodge sideways out of the line. It also stands its ground to cast Cascading Flare, erupting flames around itself for several seconds while rooted — that is your free DPS window. Whenever the red icon flashes, it punishes face-hugging with a brutal point-blank slam; keep your distance during that tell. Attack from the side to avoid frontal sweeps, and watch the tail and sword stomps.

Phase 2 — burning blade. Around half health Zmey staggers, then returns with a flame-lit sword dealing Burn damage. The move set is the same; the side-step still answers the downward swings. Rush in after each dodge to chip the bar. Build Break Damage for Riposte bursts.

Finish. With sustained melee pressure from a stealth Shell (Tiel dodging into Shadow Strike) or Genessa drawing aggro, Zmey falls faster than Malborn Offspring for most players.

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Important Notes: Side-Steps, the Flare Window, and the Red Icon

• Sideways, never backward. The Cosmic Flames line is trivially sidestepped. Retreating runs you down the beam.
• Flare = free damage. Cascading Flare roots Zmey. If you have the Seedbearer’s Scripture, this phase is near-safe DPS time. Do not waste it healing.
• Red icon = back off. The point-blank slam triggers on face-hugging. Respect the tell and reposition.
• Side attacks avoid sweeps. Frontal stomps and tail sweeps still reach you at the side; watch for them while you whittle.
• Flamebreath is an opening. When Zmey uses Flamebreath, the recovery is a clean retaliation window before its next move.
• Easier than Malborn, with prep. Multiple guides note Zmey fell easier than the Offspring when fought with a powered Tiel and the Endless Core. The difference is the no-summon rule and twin health bars on Malborn.

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Rewards, the Gloom Doorway Trap, and the NG+ Handoff

Item	Note
Zmey drop	None (the reward is story completion)
Endless Core (pre-fight)	Removes Tarforge cap; enables +17 and beyond
Post-fight	Interact with the siphoning machine in Marrow Keep; “Send Ova” starts NG+

The biggest trap near the fight is the Gloom doorway inside the Hidden Nave. A nearby doorway asks you to offer all carried Gloom; if you loot the surrounding Gloom piles first, you lose it. Deal with the doorway before vacuuming the chests. Also remember the Endless Core’s altar chest is the real prize — the doorway is a separate, greedy interaction.

After Zmey dies, the story is not over: Undermether confirms the foul passenger is gone and asks you to send the recovered kin onward. That final interaction, not the boss kill, closes the ending. Picking “Send Ova” at the Marrow Keep siphon launches New Game Plus; skip it to keep exploring.