Iron Fiend and Jade Dancer

Iron Fiend and Jade Dancer, the Young Mistress's Guardians, are the secret third phase of Phantom Blade Zero's Mu Xiaokui fight by the lake in the Village of Lu, opened by finishing the Young Mistress quest. Keep both in view, take down Iron Fiend first, parry the third hit of their combined attack, and dodge every red-glint grab. They drop the Fiend Saws and Fist Fragment: Core.

At least 44.4% of Phantom Blade Zero's Steam players had beaten Iron Fiend and Jade Dancer by Nov 9, 2026: that share had triggered Fiend-Aura Erosion with the Fiend Saws (the achievement Delayed Blast), a weapon the guides list only as this fight's drop, against 56.0% who had beaten Mu Xiaokui herself. So most players who reach the lake find the secret third phase. The two Young Mistress's Guardians fight as a pair in the lakeside reeds of the Village of Lu, and only if you finished the Young Mistress quest first; Game8 says the fight "gets significantly easier once you take down one of them", and the one to take down is Iron Fiend.

Both health bars are on screen at 4:40 of PowerPyx's Oct 29, 2026 recording of the whole Mu Xiaokui fight, labeled "Jade Dancer, Young Mistress's Guardian" and "Iron Fiend, Young Mistress's Guardian", as the pair close on Soul in the lakeside reeds.

Quick facts

Where	The reeds about 55 m past the Lakeside bell, Village of Lu, after Mu Xiaokui's second phase
Chapter	5, Heartless Remnants, by Game8
Required	No: Game8 lists them as a main boss, but they appear only after the Young Mistress quest
Health	41,680 HP each, the same on every difficulty
Rewards	Fiend Saws (Damage 302, Guard Break 120) and Fist Fragment: Core
Respawn bell	Lakeside

Five ribbons and a violet flare

Finish the Young Mistress quest, which AllThings.how says requires five ribbons (Side Quests), then beat both of Mu Xiaokui's phases, Young Mistress of the Order and Queen of Iron and Jade. A violet flare then summons the two guardians, each with its own health bar. Without the quest, the Mu Xiaokui fight ends after two phases. Sources differ on how to count them: Game8 gives the guardians a page and a place in its main boss list, PCGamesN treats them inside its Mu Xiaokui entry, and AllThings.how calls them Mu Xiaokui's secret Phase 3.

Two on one

Never lose sight of either. Game8 says to constantly reposition using directional dodges and keep both in view; AllThings.how adds that they attack together.
Isolate Iron Fiend and kill him first (Game8).
PCGamesN's alternative: "try to guard break both at the same time, or keep them apart by moving a lot".
Step away when Iron Fiend charges (AllThings.how).

Every red glint is a grab

Combined three-hit attack: when the two stand close, watch for purple effects around Jade Dancer's blades. Block the first two hits and parry the third, a blue glint, for a Ghoststep counter. Each can also do it alone, with the same timing.
Horizontal scissor kicks (Jade Dancer): a red-glint grab. Dodge, then Ghoststep counter.
Whirlwind dash (Iron Fiend): a red-glint grab. Dodge.
Tactical retreat (Iron Fiend): a red-glint grab. Dodge.
Surprise kicks (Iron Fiend): the fastest grab of the fight, with almost no startup cues. Dodge.
High knees and claps (Iron Fiend): PCGamesN's move to watch, followed by a red attack. Dodge the red attack.
Blade kicks and blue crescents (Jade Dancer): her bladed legs throw blue crescent arcs.

The Iron Jade Strike

This phase can turn into the Iron Jade Strike, a scene of four button prompts: Jade Dancer's leap (a single press makes Soul parry), the blade clash with her gauntlet (mash), Iron Fiend's grapple (mash) and the last clash with Mu Xiaokui (press or mash). The buttons change every attempt; single prompts slow the game while shown, and mashing at about one press a second is too slow. A miss throws Soul into the reeds, and the strike comes back about every 27 seconds until every prompt is cleared.

Fiend Saws and Fist Fragment: Core

The Fiend Saws are a dual wield weapon, Jade Dancer's leg blades; Weapons calls them fast, with Corrosion bursts on guard-broken foes, and Steam's Delayed Blast achievement asks you to trigger their Fiend-Aura Erosion (Trophies and Achievements). Fist Fragment: Core is one of the fragments that form the Worldbreaker Fist, used to Soul Temper the Iron Gauntlets (Phantom Edges). Puppet No. 44's Eye comes from the Mu Xiaokui fight whether or not this phase happens.