Home / All guides / Slay the Spire 2 Act 3 Enemy and Boss Guide: Knight Gang Elites, Aeonglass, Test Subject #C10 and The Queen (v0.111)

Slay the Spire 2 Act 3 Enemy and Boss Guide: Knight Gang Elites, Aeonglass, Test Subject #C10 and The Queen (v0.111)

Every Act 3 Glory enemy, elite and boss in Slay the Spire 2 (v0.111 beta): Frog Knight and Owl Magistrate loops, the five-elite pool including Mecha Knight and Soul Nexus, plus Aeonglass, Test Subject #C10 and The Queen with their final-boss cycles and answer windows.
combat Hard 19 min read 📅 2026-09-04
By the STS2 Guide Team · How we research and verify →
Fact-checked against patch notes and the community wiki. Numbers cite game v0.111 and may shift between patches.

The Act 3 spike: what Glory expects your deck to already be

Glory, the current final act, does not raise the difficulty so much as it stops subsidizing you. Two normal enemies sit at 191 and 234 HP, numbers that outrank several Act 1 bosses. The elite pool expands to five encounters, including a 300 HP Mecha Knight that the community treats as a raid boss. All three map bosses are mechanics checks where brute stats alone lose. If Act 2 asked whether your engine exists, Act 3 asks whether it exists three times over, in the same run, without a shop between failures.

The pool composition, from our v0.111 database: normals are Frog Knight and Owl Magistrate; elites are Magi Knight (82), Spectral Knight (93), Flail Knight (101), Mecha Knight (300) and Soul Nexus (234); bosses are Aeonglass, Test Subject #C10 and The Queen. Note what is absent: nothing here is a simple stat body you can race by default. Every single fight, down to the normals, carries a mechanic that punishes a specific deck shape, and the act tip our database records says to pre-plan answers: damage over time for the loop boss, multi-hit for stack-strip checks, burst for scripted windows.

The spike shows up concretely in three numbers. Block demands jump: 29 on turn one against Soul Nexus, 33 on Owl Magistrate's Verdict turn, 35 repeatedly against Mecha Knight and Frog Knight's charge. Damage demands jump: 600 total HP on Test Subject #C10 and roughly 400 plus a 199 guard on The Queen. Punishment density jumps: three of the five elites apply auras or statuses that degrade your cards themselves, not your HP bar.

What deserves emphasis is that this act is still fully telegraphed. Fixed loops run on schedules: Owl Magistrate repeats every four turns, Mecha Knight every four, Soul Nexus under a no-repeat rule you can exploit. Our mistakes page lists ignoring intents among the most common causes of death in the game, and Act 3 is where that habit cashes out, because the schedules here are the fight. Learning them is most of the win rate.

One orienting fact so you plan the ending correctly: the Architect, encountered after Act 3, is a scripted story encounter rather than a fight, so the bosses below are the last real combat checks of the run. Beat whichever one the map rolls and the climb is functionally done. Everything in this guide is written against v0.111 beta, with the usual Early Access caveat: where a number comes from a single community source, it is flagged as such in the section that uses it.

Frog Knight: 15 Plating and the half-HP beetle tripwire

Frog Knight is the softer of the two Act 3 normals at 191 HP, and it teaches the act's first lesson immediately: damage shape matters more than damage total. It carries 15 Plating, a per-hit damage reduction, which means a flurry of small hits gets shaved down on every swing while one big attack pays nearly full price. A deck of chips will mathematically lose to this frog even with excellent card quality; a deck with a few heavy hits walks through it.

The action cycle is a three-move rotation. A 13-damage tongue lash that applies Frail, cutting your future Block gains. A 21-damage smite, the heaviest normal-fight single hit in the act. And a war cry granting itself 5 Strength, which is the timer on the whole encounter: leave it alive through two or three war cries and even your good Block turns start leaking.

The tripwire is the one that ends runs. Below half HP, Frog Knight unleashes a one-time 35-damage beetle charge. It happens exactly once, and it happens the moment you push it under roughly 95 HP. The database tip is explicit: have 35-plus Block ready on the turn you push it below half. This converts the fight from a race into threshold management, the same discipline Ceremonial Beast demanded in Act 1 but with a bigger number and no phase debuff attached. Cross the line on a turn when you have already spent your energy attacking, not on a turn when your hand is empty of defense.

Per-character shape advice. Ironclad is comfortable: his Strength scaling multiplies into big single hits that punch through Plating, and Body Slam converts a defensive turn into exactly the heavy hit this fight wants. Silent should de-emphasize Shiv flurries here and lean on Poison, which ignores Plating entirely as damage over time. Defect wants Frost-fed Block for the smite turns and evocations timed after the war cries. Regent's Sovereign Blade line, usually awkward into capped enemies, is actually excellent here because nothing caps damage. Necrobinder can simply Doom through it, though note the execute threshold interacts with nothing special here, it is just a clean kill.

Also respect the Frail. Two stacked tongue lashes turn a 20 Block card into a 14 Block card, which is the difference between covering the 21 smite and eating 7. Cleanse Frail if you have the tool, otherwise bias your Block turns one card earlier than feels necessary. And if you meet Frog Knight while low on HP with no Block potion left, remember the tripwire rule applies to the enemy's HP, not yours: it charges the moment its bar crosses half, ready or not.

Owl Magistrate: a four-turn loop you can solve in your head

Owl Magistrate, 234 HP, runs the most legible script in the act, a fixed four-turn loop that repeats for the entire fight. Turn one is Scrutiny for 16. Turn two is a 4-hit peck for 6 per hit, 24 total. Turn three is Ascend, a defensive turn that deals nothing to you. Turn four is Verdict, 33 damage plus 4 Vulnerable. Then the loop restarts. Because it never deviates, this fight is effectively an open-book exam, and passing it is about scheduling rather than reaction.

Block planning writes itself. You need real Block on turns one, two and four; nothing on turn three. The peck turn deserves special respect: four hits of 6 means Weak shaves 25 percent off all four swings, and Plating-style effects (Heart of Iron potion grants 7 Plating) subtract from each hit individually, so per-hit mitigation is worth four times its face value. Intangible answers it even harder, reducing all four hits to 1 each, and Ghost in a Jar exists precisely for turns like this on Silent.

The Ascend turn is your free aggression turn, and using it well is the whole tempo of the fight. A defensive enemy turn plus no incoming damage equals the act's gift: dump setup powers, banking resources, or your heaviest attack package here every cycle. The database tip is exactly that, deal your damage during Ascend, and hold 33-plus Block on Verdict turns. Loop-aware play converts this 234 HP wall into roughly three free turns per cycle where you pay nothing for aggression.

The Vulnerable rider on Verdict is the hidden tax. Four stacks of Vulnerable left standing means the next Scrutiny and peck turns hit 50 percent harder, so either Block through Verdict and accept chip damage, or bring an Artifact charge to eat the debuff, or plan your damage so the fight ends before the third loop. Long fights against this boss are not lethal because of Verdict itself; they are lethal because of what Verdict's Vulnerable does to the following loop.

Deck-fit notes: this is a showcase fight for burst decks that were waiting for a telegraphed window, Star-bank Regent releases on Ascend, Defect Dark orb evocations timed to the free turn, Ironclad Demon Form scaling with the safe turn absorbing the tempo cost. Grind decks win too, slower and safely, provided they hit the 33 Block mark every fourth turn without exception. The kill condition either way is simple arithmetic: 234 HP divided by your per-cycle damage during Ascend and the spare capacity of the other three turns. If that division says six-plus cycles, upgrade something at the campfire first.

The Knight Gang: Magi, Spectral and Flail, in that order

Three of the act's five elites arrive together as the Knight Gang, and two of them attack your cards instead of your body. Magi Knight, 82 HP, carries Aura Dampen: while it lives, every card in your hand is Downgraded, a weaker version of itself. Spectral Knight, 93 HP, carries Aura Hex: while it lives, every card in your hand becomes Ethereal, so unplayed cards vanish at the end of your turn rather than waiting in your discard pile. Flail Knight, 101 HP, the tankiest of the three, plays honest attrition offense: it opens with a 15-damage Ram, then cycles Breaker for 3 Strength, Flail hitting twice for 9, and more Rams.

The auras reframe the whole fight. Downgraded means your entire deck runs below curve until its source dies, every Block slightly smaller, every attack slightly weaker. Ethereal is crueler to specific archetypes: combo decks holding pieces for the right turn, Star-banking plans that want to wait, any hand where the good cards arrive in the wrong order. Against Spectral the rule is play it or lose it. Flail Knight degrades nothing; its entire threat is the slow Strength stacking that eventually overwhelms a tired Block plan.

So the kill order is fixed, and our database records it as a strict sequence. Magi Knight dies first: the lowest HP body in the gang, and one kill removes the global Downgrade plus the 35-damage Magic Bomb it cycles toward, the biggest single hit in the encounter. Spectral Knight dies second, right after Magi, freeing your hand from Ethereal before the long cleanup. Flail Knight dies last, and left for last it is a scripted dummy a half-spent deck can still beat: full information, no statuses, just cycle Block against its known rotation. The reverse order is strictly worse, because every turn an aura knight lives is a turn your cards themselves are worse, and card quality is worth more than the HP you save by tanking Flail first.

Practical notes by phase. While both auras are up, fight in survival mode: cheap cards, fast commitments, no greed. The moment Magi dies your damage returns to full; the moment Spectral dies your hand management normalizes. In the Flail mop-up, the double Flail at 9 plus 9 splits across two hits, so Plating and Intangible overperform against it while Weak shaves a clean quarter off both swings, and the Rams want real Block. The gang is also one of the best potion fights in the act, a three-elite gauntlet in one encounter: Strength Potion the moment the Magi aura drops so your cards hit full value, Weak Potion before Flail's heavy turns, and Gremlin Horn triggers three times here, effectively funding the back half of the fight.

Two closing cautions. Area damage hits all three bodies, which is real HP value, but it delays the aura kills and the auras are worth more than the HP: use AoE incidentally while focusing Magi, never as the plan. And per-character fit: Silent suffers least from Ethereal because Shiv and Sly discard plans play cards rather than hoard them, Ironclad can simply pay the Downgrade tax and keep swinging, Defect loses the most to Ethereal since orb setup wants held cards for evoke timing, and Necrobinder barely notices. Whatever the class, the order stands.

Mecha Knight: the deadliest elite, one turn at a time

Mecha Knight is 300 HP of scheduled violence, widely considered the deadliest elite in Early Access, and it comes with a data honesty flag our database attaches directly to the entry: single-source community data, verify in game. With that caveat on the table, the documented profile is still the best planning tool available, and it is a clean four-turn loop.

Turn one is Charge for 25. Turn two is Flamethrower, shoving 4 Burns into your hand. Turn three is Windup, granting itself 5 Strength and 15 Block while doing nothing to you. Turn four is Heavy Cleave for 35. Then the cycle repeats, with the accumulated Strength making every subsequent pass heavier. It also carries 3 Artifact, so the first three debuffs you throw at it, Weak, Vulnerable, anything, bounce off. Budget your debuffs accordingly or waste them entirely.

The Burns are the fight's silent killer. Four Burn junk cards in your hand on the Flamethrower turn clog every draw for the rest of the fight, and unplayed Burns sitting in hand are damage you took for nothing. The database rule is to play or exhaust them immediately, and decks with exhaust outlets, Ironclad's True Grit and Corruption lines, Charon's Ashes turning each exhaust into 3 damage to all enemies, convert the liability into fuel. Decks without exhaust outlets need to simply pay the 1 energy to play Burns out on quiet turns, ideally the Windup turn.

Windup is your scheduled decision point. The enemy gains Strength and Block and deals nothing, so the naive read is free aggression turn. The database tip says otherwise and it is right: skip attacking on Windup turns, because your damage is bouncing off the fresh 15 Block plus whatever it has banked, and this is the turn to dump Burns, set up powers, heal, or bank Stars for the coming Cleave. Hold 40-plus Block for Heavy Cleave, because 35 base damage plus the Strength it has stacked by mid-fight is exactly the number that one-shots tired runs.

Who should fight it, honestly: decks with scaling answers, heavy Block, and exhaust or hand-fixing tools. Undercooked decks should skip it, our database says so in almost exactly those words, and this is one of the only elites in the game where skipping is a respectable plan rather than a confession. The 300 HP body under a fixed loop is beatable by design, but it prices a mistake at 25 to 35 HP each, and Act 3 rarely forgives three of those in a row. If your map offers Soul Nexus or the gang instead, take them with a weaker deck and come back only when the engine is real.

Soul Nexus: respecting a 29-damage opener and the no-repeat rule

Soul Nexus, 234 HP, opens every single fight with Soul Burn for 29 damage, before you have played a card. That is the single largest scripted turn-one hit on any non-boss in the game, and it means your opening hand wants Block in it, not damage. Mulligan logic barely exists in this game, so the practical planning happens before the fight: enter with a Block potion or a cheap Block card you trust, because eating 29 on turn one against a 234 HP elite is how runs start dying.

After the opener it cycles three moves without ever repeating the same one back to back: Soul Burn at 29, Maelstrom hitting four times for 6, and Drain Life for 18 damage plus 2 Vulnerable and 2 Weak. The no-repeat rule is exploitable intelligence. If Soul Burn just landed, the next turn is guaranteed to be Maelstrom or Drain Life, never a second 29. You can plan your Block spending in waves: full armor into Soul Burn turns, per-hit mitigation into Maelstrom turns, and partial Block plus debuff awareness into Drain Life turns.

The multi-hit analysis favors the usual tools: Weak cuts all four Maelstrom hits by a quarter, Plating subtracts from each swing, Intangible floors the entire volley at 4. Ghost in a Jar on Silent single-handedly answers a Maelstrom turn. Drain Life's riders are the long-term problem, since 2 Vulnerable inflates every future Soul Burn and 2 Weak deflates your retaliation; the database tip specifically calls out debuff-cleansing relics in the Orange Pellets style as a huge edge here, and Artifact charges saved for the Drain turn deny both riders outright.

Soul Nexus as a deck check: it is the purest Block-floor exam in the act. There is no phase change, no summons, no card degradation, no threshold tripwire. It does the same three things forever, harder than most elites, and the fight is simply whether your defensive engine covers a rotating 18, 24 and 29 for the six-plus turns a 234 HP kill requires. Frost-turtle Defect, Block-scaling Ironclad and Wraith Form Silent all profile beautifully; glass cannon decks that spent Act 3 gold on damage discover that turn one charges 29 HP of admission and the price repeats.

One closing timing note: because the cycle never repeats, the fight's deadliest stretch is predictable. Count moves from the opener: Soul Burn, then two non-Soul-Burn turns, then it can return. Keeping that three-turn rhythm in your head lets you spend Block efficiently on the in-between turns instead of panic-blocking every turn at full price, which is exactly the efficiency margin that decides whether a mid-tier deck survives this elite or bleeds out to it.

Aeonglass: the loop boss and its phase-two stun window

Aeonglass is the newest Act 3 boss, and its history matters for how you read this section. It replaced Doormaker in v0.105, was reworked alongside Infested Prism in v0.106, and was nerfed as recently as v0.109. Our v0.111 database documents the current boss slot as Aeonglass while its detailed mechanics entry still carries the Doormaker lineage data, so treat this section as the best-supported picture available and verify fine numbers in game, the same caveat we apply to all post-rework bosses.

The core identity is the loop: a 155 HP door that does not stay dead. The fight cycles door phases and creature phases in a three-phase rotation that dates to the v0.101 rework of Doormaker. You break the door, creatures come out, you kill the creatures, and the door respawns at full HP with its Strength carrying over from the previous cycle. That last clause is the fight's real clock: every loop you fail to close cleanly leaves the next loop's door and creatures hitting harder, so a slow deck is not merely slow, it is escalating its own problem.

The documented answer window is the phase-two stun: a full turn where the encounter is stunned and cannot act. That turn is the best moment in the fight, and spending it on chip damage wastes it. The correct uses are setup and breath: powers, banking, healing, hand-fixing, preparing the burst that closes the current creature phase. Poison and other damage over time shine here per our database tip, and the reason is mechanical: Poison persists across the phases while the door respawns, so stacks you apply in one phase keep ticking into the door of the next, compounding across the whole loop structure instead of resetting like your burst damage does.

That persistence distinction organizes the whole strategy. Damage over time is the engine that profits from the loop; front-loaded burst is the tool that closes creature phases before the Strength carryover compounds; raw endurance loses, because the respawning door outlasts any finite Block plan. Noxious Fumes Silent profiles as the premium matchup, Necrobinder Doom lines are strong with the standing v0.108 note that Doom executes at end of turn, and Strength-scaled multi-hit decks can substitute volume for persistence if they close phases fast.

Practical loop discipline: treat each door break as a checkpoint, not a victory. Before you break the door, set your board: powers down, Poison ticking, Block ready for the creature opener. Breaking the door with nothing prepared hands the initiative back to the encounter and starts the next cycle at a disadvantage, and because Strength carries over, every wasted cycle is permanently more expensive than the last. Aeonglass punishes improvisation more than it punishes weakness, which is a fitting final exam for an act built on schedules.

Test Subject #C10: three phases, 600 HP, DoTs that reset

Test Subject #C10 is a 600 HP marathon delivered as three phases at 100, 200 and 300 HP, and it is the fight where knowing what each phase punishes turns an impossible wall into three separate, solvable problems. The single most important global rule: damage over time resets between phases. Poison banking, Doom stacks, anything you were amortizing across the fight gets wiped at each transition, so every phase must be won by the tools that still work inside it.

Phase one, 100 HP, punishes skills: playing Skills grants it 2 Strength each time. The answer is to lean on Attacks and Powers during this phase, saving your Skill package entirely if the deck can afford it. A deck that habitually opens with draw-and-Block Skills feeds the boss 4 to 6 Strength before phase two even begins, and that Strength is permanent for the rest of the marathon. Think of phase one as a tax on your habits specifically.

Phase two, 200 HP, shoves Wounds into your deck for unblocked damage, meaning every point of its damage you fail to Block converts into future hand clog. The database instruction is perfect Block in phase two: this is where your Block engine earns its slot, where Block potions belong, and where exhaust outlets convert forced Wounds into fuel rather than dead draws. Leaking 8 damage here is not an 8 HP mistake, it is an 8 HP mistake plus a Wound in every future shuffle of a very long fight.

Phase three, 300 HP, alternates Intangible turns, reducing all damage it takes to 1. The rule is to strike only on vulnerable turns: when Intangible is up, do not attack at all, Block and prepare, and when it drops, unload. Multi-hit attacks that would waste themselves into Intangible get banked a turn; big single hits get scheduled for the windows. This is the phase where the database note that scaling powers win the fight pays out, because by now your engine is the only thing still producing full-value turns.

Pacing the marathon: 600 total HP with three mechanic shifts means you cannot win on front-load, and you cannot win on attrition alone either. The composite profile is a deck with a real Block engine for phase two, discipline to hold Skills in phase one, and scaling that peaks in phase three. Potions are phase-two insurance above all: the temptation is to spend them early on the 100 HP bar, and the correct read is that phase two's perfect-Block demand is where Block and defensive potions carry the most risk reduction. Character-wise, Frost Defect and Block-Ironclad handle phase two best, exhaust builds eat the Wound problem alive, and Poison players must simply accept the two resets and re-apply per phase rather than banking.

The Queen: Bound chains, the 99-debuff turn and the Amalgam rule

The Queen is the act's final exam and the least documented boss in our file, roughly 400 HP behind a 199-point guard, with our database explicitly flagging the HP figures as single-source and uncertain. The mechanics that are documented, however, form a coherent and vicious kit, and the fight has a strict rule order like the Knight Gang taught you.

The signature mechanic is Chains of Binding: the first cards you draw each turn arrive Bound, and only one Bound card can be played per turn. Your opening hand is therefore rationed, one chosen card from the Bound group per turn. The documented escape hatch is that mid-turn draw is unrestricted: cards you draw during your turn, through Acrobatics, Offering-style effects, or any draw triggered after your turn begins, are not Bound and play freely. The Queen is thus a puzzle about converting your turn's energy into mid-turn draw, and the database tip is to burst her down with exactly that.

Turn two is the other headline: a slam of 99 stacks each of Weak, Vulnerable and Frail. No Block in the game matters against it, it is a debuff nuke. Artifact answers it, one charge denies the entire package, which makes Artifact effects and artifact-granting relics the single best prep for this boss. Without an answer, plan to absorb it: your damage drops a quarter, your damage taken rises half, your Block generation wilts under Frail, and you survive the stretch on pre-placed Block and hp you banked for exactly this.

Then the Amalgam rule. The Queen fights alongside her Torch Head Amalgam (buffed in v0.109, so respect it more than older videos suggest), and when the Amalgam dies she Enrages into an Execution loop. The kill order is counterintuitive but recorded plainly: kill the Amalgam first anyway. Phase one with a living Amalgam is your setup phase, the calm stretch where scaling powers go down and resources are banked; the Enrage that follows is the fight's endgame burst window, and you want to enter it with your engine already standing and a mid-turn draw plan ready to spend everything.

The composite game plan: phase one is for powers, Amalgam removal triggers the Execution loop on your terms, Artifact or a planned absorb handles the 99 turn, and the finish comes from unrestricted mid-turn draws converting banked energy into a burst she cannot Bound. Regent's Star bank is the dream finisher, Silent's Acrobatics engine is the dream opener, Ironclad simply out-stats the check if the Block holds, and Doom profiles well into the percent thresholds as long as you respect the v0.108 end-of-turn resolution. She is beatable, but only on preparation, which is precisely what a final boss should test.

Answer windows: mapping every Act 3 check to a tool

Act 3 is winnable at the map screen, by checking whether your run owns an answer for each mechanic before you commit to a path through the elite cluster. Here is the full map, mechanic to tool, compressed for a final read.

Damage shape checks: Plating on Frog Knight wants single big hits or damage over time; the Knight Gang's Skittish-free bodies want focus fire in the fixed order Magi, Spectral, Flail; Mecha Knight's Windup Block wants you to not attack that turn at all. Hand degradation checks: Ethereal from Spectral wants cheap playable cards, Downgrade from Magi wants raw stat quality that survives a tax, Burns from Mecha want exhaust outlets or the discipline to pay them out on quiet turns.

Block floor checks, listed as the numbers your deck must be able to produce: 16, 24 split as 4 times 6, and 33 on the Owl loop; 35 for the Frog tripwire and Mecha Cleave, meaning 40-plus to be safe; 29 on turn one into Soul Nexus; and effectively unlimited patience against the Queen's Execution loop. Per-hit mitigation overperforms everywhere the damage splits (Maelstrom, Soul Flame, Flail, the peck), so Heart of Iron, Plating relics, Intangible potions and Weak are disproportionately valuable this act. The Weak Potion specifically belongs on telegraphed 33 and 35 turns.

Boss kit checks: Aeonglass wants damage over time that persists across its phase loop and discipline setting up before each door break; Test Subject #C10 wants Attack-heavy phase one, perfect Block phase two, window striking phase three, and zero reliance on DoT banking; the Queen wants Artifact for the 99 turn, mid-turn draw for the Bound chains, and Amalgam-first kill order. Notice that no single deck answers all three bosses perfectly, and that is by design: the act rewards knowing which checks your specific build passes and pathing accordingly, plus the potion and relic flexibility to patch one hole.

Resource timing rules for the finale: potions are for the elite that is actually on your path, not for a hypothetical boss; campfire upgrades beat rests when your HP is above the act's per-fight bleed rate; and Fairy in a Bottle is at its best insurance value across exactly these five elites and three bosses. The Architect after the act is scripted story, not combat, so nothing after The Queen's door demands a saved potion.

Close the loop with the earlier acts' lessons and the run finishes itself: Act 1 taught schedules and thresholds, Act 2 taught engines and target commitment, Act 3 asks you to apply both at speed against the steepest numbers in Early Access. When the map rolls your boss, reread that boss's section, count your answers, and path to the campfire that funds them. That habit, more than any individual tech card, is what carries decks through Glory in v0.111.

Pro tip: Treat Act 3 bosses as question papers: Aeonglass asks for damage over time, C10 asks for a phase-by-phase plan, the Queen asks for Artifact plus mid-turn draw. Check which question your deck can actually answer at the map screen, because no single build answers all three.