Slay the Spire 2 Boss

Rocket Boss Guide

Boss • Act 2 - Hive
Base HP
199
Ascension HP
209
Moves
5
Encounters
1
Boss Strategy

How to Beat Rocket

Quick Strategy

Treat Kaiser Crab as a facing and kill-order fight, not simply a two-target damage race. Crusher and Rocket surround you, and the enemy behind you deals 50% more damage, so targeted cards and potions also function as positioning tools. Rocket is normally the first kill because its turn-four Laser hits for 35 on Ascension, while Crusher applies Weak and Frail before that window and continues scaling. Ideally kill Rocket before the first Laser; otherwise survive the first one and finish Rocket before the second. If your deck can reliably cover Laser, killing Crusher first becomes a valid alternative. Before killing either enemy, remember that the survivor gains 6 Strength and 99 Block.

What This Fight Tests

Reliable turning

You can only face one side at a time, while the enemy behind you deals 50% more damage. A deck needs enough targeted cards, potions, or other controllable effects to face the dangerous attacker when the large hit actually arrives.

First Laser

Rocket reaches a 35-damage Ascension Laser on turn four. Crusher has already applied Weak and Frail by this point, so an otherwise normal defensive hand can be much less effective than expected.

Kill order

Rocket is usually the priority because removing the 35-damage repeating threat simplifies the fight dramatically. Crusher-first becomes attractive only when Rocket damage is already consistently controlled and Crusher scaling or debuffs are the larger long-term problem.

Post-kill transition

Killing one enemy immediately changes the remaining fight because the survivor gains 6 Strength and 99 Block. The current intent matters: removing Rocket while Crusher is about to multi-hit can create a much more dangerous attack than the pre-kill numbers suggest.

Key Decisions

Face the dangerous attack, not automatically your damage target

My facing decision is based on incoming damage first. I may still be focusing Rocket for the kill while temporarily targeting Crusher with another card or potion if Crusher is the attack I need to reduce. Target selection is both an offensive decision and a defensive positioning mechanic in this fight.

A non-damage targeted card can still solve facing

Turning does not require dealing damage. A targeted defensive card or a targeted potion can rotate you toward that enemy, so I count those effects as part of the deck’s Kaiser Crab defense instead of evaluating only targeted Attacks.

Random and AoE effects are not reliable turning tools

An effect dealing damage to an enemy does not automatically mean it controls facing. Random-target effects and untargeted AoE do not give the same reliable turn control, so I still want at least one deliberate targeting line for the important attack turns.

Rocket first is the default, not an absolute rule

Most decks should pressure Rocket because its Laser creates the largest early defensive check. But if the deck can repeatedly block that hit while Crusher’s Weak, Frail, and Strength scaling are becoming the true problem, Crusher-first can be the better route.

Do not take lethal on one enemy without checking the survivor

The surviving enemy gains 6 Strength and 99 Block. Before taking lethal, I look at the survivor’s current or next intent. Removing one half of the encounter is good, but doing it immediately before a dangerous multi-hit can create a larger hit than simply waiting one turn.

Combat State

Innate Powers

Back Attack
Starts combat with this power
1 →
Crab Rage
Starts combat with this power
1 →
Combat Data

Moves

5 moves

Targeting Reticle

Attack
TARGETING_RETICLE
Damage
3 → 4

Precision Beam

Attack
PRECISION_BEAM
Damage
18 → 20

Laser

Attack
LASER
Damage
31 → 35

Recharge

Sleep
RECHARGE
Enemy AI

Attack Pattern

Cycle

Targeting Reticle → Precision Beam → Charge Up → Laser → Recharge → repeat

Initial move: Targeting Reticle
View pattern states
Targeting Reticle
move
Next: PRECISION_BEAM_MOVE
Precision Beam
move
Next: CHARGE_UP_MOVE
Charge Up
move
Next: LASER_MOVE
Laser
move
Next: RECHARGE_MOVE
Recharge
move
Next: TARGETING_RETICLE_MOVE
Fight Plan

Rocket Fight Plan

The raw move pattern tells you what is coming. This plan focuses on what I want the deck to accomplish before each dangerous part of the fight.

Phase 01

Choose the Rocket plan

Establish enough damage to pressure Rocket while keeping deliberate control over which enemy you are facing.

  • Start by identifying which cards and potions can deliberately target each side. Do not wait until Laser turn to discover that the hand cannot rotate you.
  • Default damage toward Rocket unless the current deck has a specific reason to pursue Crusher first.
  • Do not waste a targeted utility card just because its damage or Block value looks small. The ability to control facing can be the more important part of the play.
  • Track Crusher’s debuff cycle while pressuring Rocket. Weak and Frail change how much damage and Block the deck can produce before Rocket reaches its largest hit.
Watch for
  • Using all targeted cards early and entering the next dangerous turn with only random or AoE effects.
  • Splitting damage evenly between Crusher and Rocket without a clear kill-order reason.
Phase 02

Debuffs into Rocket Laser

Reach Rocket’s first Laser with enough effective defense and the correct facing, then convert the following window into the first kill.

  • Account for Crusher’s Weak and Frail rather than evaluating the Laser turn from printed Block values alone.
  • Face Rocket before its Laser if Rocket is the dangerous attacker. Because back attacks deal 50% more damage, the difference between correct and incorrect facing is enormous on a 35-damage base hit.
  • Use a defensive potion here when necessary. Covering one Laser can buy exactly the extra cycle required to finish Rocket afterward.
  • If Rocket survives the first Laser, make its second Laser a hard deadline unless the deck has demonstrated that it can repeatedly handle the hit.
Watch for
  • Planning to block 35 while forgetting that Frail reduces the practical defensive output of the hand.
  • Facing Crusher because the previous card targeted it and then ending the turn without correcting direction before Rocket attacks.
Phase 03

First kill and transition

Remove one enemy without creating a lethal 6-Strength transition, then cleanly finish the survivor.

  • Before killing Rocket, inspect Crusher’s current intent. If Crusher is about to multi-hit, the immediate +6 Strength can make that turn much more dangerous.
  • Before killing Crusher, make sure the same Strength gain does not turn Rocket’s upcoming attack into an unacceptable hit.
  • Expect 99 Block on the survivor and avoid calculating the second kill as though damage continues uninterrupted.
  • Once the first enemy is dead and the transition turn is covered, simplify the fight. One remaining target is substantially easier to manage than the original surround mechanic.
Watch for
  • Taking an attractive lethal without checking the survivor’s attack pattern.
  • Assuming the second enemy dies immediately afterward despite the 99 Block gain.

Dangerous Turns & Windows

Danger Window
Facing away

Crusher and Rocket begin on opposite sides, and the enemy behind the player deals 50% more damage. You cannot face both simultaneously.

Response: Use deliberate targeted cards or potions to face whichever attack is currently more dangerous. Treat rotation as part of defensive sequencing rather than an afterthought.
Danger Window
Crusher Bug Sting

Crusher’s Bug Sting deals 6 × 2 normally or 7 × 2 on Ascension and applies both 2 Weak and 2 Frail. Those debuffs arrive shortly before Rocket’s largest early attack.

Response: Plan the Rocket defensive window using your debuffed output. Do not assume your normal Attack and Block efficiency will still be available.
Danger Window
Rocket Laser

Rocket uses Laser for 31 damage normally and 35 on Ascension after Charge Up. Facing away from Rocket makes an already large attack substantially worse.

Response: Face Rocket, reserve dense defense or mitigation, and use a defensive potion if that one turn is the only obstacle between the deck and killing Rocket.
Danger Window
Crusher scaling

Crusher uses Adapt to gain Strength and also carries the debuff pressure that makes the Rocket side harder to defend. Allowing both enemies to remain alive for repeated cycles steadily increases the encounter burden.

Response: Use Rocket as the default first kill, but if Laser is already solved and Crusher scaling is the real long-term failure mode, reevaluate the kill order instead of following the default blindly.
Danger Window
Crab Rage transition

When one member of the encounter dies, the survivor gains 6 Strength and 99 Block. The Strength gain applies immediately enough that a pending multi-hit can become dramatically more dangerous.

Response: Take lethal only after checking the survivor’s current intent. Sometimes delaying the kill by one turn is safer than triggering the Strength gain immediately before its strongest attack.
Before the Fight

How to Prepare for Rocket

I use these checks before committing the final rewards, upgrades, shop purchases, and potions leading into the Boss.

TargetingCritical

Can I deliberately turn toward either enemy?

Ready when

The deck has enough targeted cards, targeted defensive effects, or potions that the player is not dependent on drawing one specific Attack to control facing.

Warning

Random-target effects and untargeted AoE do not provide reliable facing control, even if they deal useful damage.

Rocket defenseCritical

What is my answer to the first Laser?

Ready when

The deck can either kill Rocket before turn four or deliberately face it and produce enough Block, Weak, mitigation, HP, or potion support to survive the 35-damage Ascension hit.

Warning

Crusher’s Frail can make a Block total that normally looks sufficient fall short on the exact turn where Rocket hits hardest.

Single-target damageHigh

Can I actually remove Rocket instead of splitting damage?

Ready when

The deck has enough controllable single-target damage to pressure Rocket through the first cycle and ideally prevent a second Laser.

Warning

Large amounts of total AoE damage can still leave both enemies alive long enough for the fight’s dangerous mechanics to repeat.

Kill transitionHigh

Can I survive the +6 Strength survivor?

Ready when

The deck can choose a safe lethal turn rather than killing one enemy immediately before the survivor’s most dangerous intent.

Warning

The fight does not simply become half as dangerous when the first enemy dies. The survivor immediately becomes stronger and gains 99 Block.

Debuff toleranceHigh

Can I function through Weak and Frail?

Ready when

The deck has enough damage scaling and defensive density that Crusher’s debuffs do not completely break the Rocket Laser turn.

Warning

Weak and Frail are especially punishing here because the encounter simultaneously demands fast damage and one dense defensive answer.

PotionMedium

Can one potion cover Laser or fix facing?

Ready when

A defensive or targeted potion has a defined job: survive one Rocket Laser, rotate toward the dangerous side, or supply the damage needed to remove one enemy before another cycle.

Warning

This fight often becomes easy after the first enemy dies, so spending a potion to cross that one transition is frequently better than saving it for an undefined future fight.

Character Matchups

Rocket by Character

The Boss does not change between characters, but the part of the fight that matters most often does. These notes focus on what each character should adjust rather than repeating the general strategy.

Ironclad should pay special attention to deterministic targeting. The encounter rewards knowing exactly which side the final targeted action leaves you facing, while effects such as Stampede can interfere with that plan by turning you unpredictably. Strong frontloaded single-target damage is valuable because removing Rocket quickly avoids repeated Laser checks.

Prioritize
  • Use deliberate targeted cards to establish the correct facing before the dangerous Rocket turn.
  • Pressure Rocket with concentrated damage rather than spreading damage without a kill-order purpose.
  • Treat Stampede and other uncontrolled targeting as a positioning risk when the final facing of the turn matters.
  • If the deck cannot kill before Laser, reserve enough Block, Weak, HP, or potion support for one large defensive turn.
Watch for
  • Assuming a random attack will leave you facing the enemy you intended.
  • Using every high-damage card before checking which side the final targeted action points you toward.

Necrobinder has a particularly useful Kaiser Crab tool because a targeted defensive card such as Defy can rotate the character without requiring an offensive play. That gives the deck more ways to face Rocket for Laser or Crusher for another dangerous attack while still advancing defense.

Prioritize
  • Count targeted defensive cards as facing tools, not only as Block cards.
  • Use Defy or another deliberate target when changing direction is more important than squeezing out another attack.
  • Keep enough controllable damage on Rocket that the fight still moves toward removing the major Laser threat.
  • Check Crusher’s current intent before taking Rocket lethal because Crab Rage can make the survivor’s next attack substantially stronger.
Watch for
  • Using a targeted defensive card early and then ending the turn after another effect rotates you away again.
  • Overvaluing passive or summon output while lacking a deliberate way to control facing.

Regent needs to separate raw output from facing control. Bombardment can create strong damage but can also rotate the character unpredictably, which is dangerous when Rocket Laser or another large attack requires ending the turn toward a specific side. Keep at least one deliberate targeting option available when positioning matters.

Prioritize
  • Do not let Bombardment determine the final facing on a dangerous attack turn unless the result is guaranteed.
  • Use deliberate targeted actions after random effects when possible to restore the correct direction.
  • Concentrate enough damage on the intended first kill instead of allowing resource generation to become slow split damage.
  • Before triggering Crab Rage, make sure the surviving enemy’s strengthened intent remains survivable.
Watch for
  • Ending the turn facing the wrong direction because Bombardment changed orientation after the planned targeted play.
  • Generating plenty of resources while both enemies remain alive through another full Rocket cycle.
Failure Analysis

Common Rocket Mistakes

These are the decisions that can make a deck look strong on paper but still fail this specific fight.

01

Splitting damage without a kill-order plan

You attack whichever target is easiest to hit each turn and gradually lower both health bars.

Why it fails

The encounter is much easier after one enemy dies. Leaving both alive preserves the surround penalty, Crusher debuffs and scaling, and Rocket’s repeating Laser threat simultaneously.

Better decision

Default to concentrating damage on Rocket unless your deck has a clear defensive reason to kill Crusher first.

02

Treating targeting as only an offensive choice

You select targets based only on which enemy you want to damage.

Why it fails

Targeting also changes facing. The enemy behind you deals 50% more damage, so an otherwise correct damage sequence can end in the wrong defensive position.

Better decision

Sequence the turn around the final facing you need. A utility card or potion may be the correct last targeted action even when it contributes little direct damage.

03

Assuming AoE or random damage turns you

You count an AoE or random-target card as your way to rotate toward Rocket or Crusher.

Why it fails

Those effects do not provide reliable intentional facing control. The damage can resolve while you remain oriented toward the wrong enemy.

Better decision

Keep an explicitly targeted card or potion available for important positioning turns.

04

Rushing Rocket without a first-Laser plan

You spend every turn attacking Rocket because it is the normal priority, but fail to kill before Laser and have no resources left to block it.

Why it fails

Rocket-first is a kill-order strategy, not permission to ignore defense. A failed race can leave you taking the largest early hit while Frail and facing pressure are already active.

Better decision

If first-Laser lethal is not realistic, preserve enough defense or potion value to survive once, then finish Rocket before the next one.

05

Killing one enemy into a dangerous survivor intent

You take lethal immediately because removing one target appears automatically safer.

Why it fails

The survivor gains 6 Strength and 99 Block. If it is currently using a multi-hit attack, that Strength gain can dramatically increase the incoming damage on the same transition.

Better decision

Check the survivor’s current intent before lethal. When necessary, delay the kill until the strengthened transition happens on a safer turn.

06

Forcing Rocket-first when the deck already solves Laser

You follow the default kill order even though the deck can comfortably cover Rocket’s big hit while Crusher’s debuffs and scaling are the real reason the fight is deteriorating.

Why it fails

Default strategy is based on the average deck. A deck with unusually strong single-hit defense can remove the reason Rocket is normally the urgent target.

Better decision

If Laser is consistently solved, consider Crusher-first and remove the enemy that is actually scaling the fight against your deck.

07

Saving a defensive potion past the important Laser

You take heavy damage on the first Rocket Laser while keeping a potion because you expect a more valuable use later.

Why it fails

Surviving one Laser often gives enough time to kill Rocket, after which the encounter becomes much simpler. That one turn may be exactly what the potion is for.

Better decision

Assign the potion to the first Laser before combat when your normal Block cannot cover it reliably, and spend it when that condition appears.

Entity Relationships

Appears In

1 encounter

Kaiser Crab

Boss
Act 2 - Hive →
Other Monsters
Crusher →
Game ID: ROCKET Data version: v0.107.1 · Main Type: Boss