Slay the Spire 2 Boss

Waterfall Giant Boss Guide

Boss • Act 1 - Underdocks
Base HP
240
Ascension HP
250
Moves
8
Encounters
1
Boss Strategy

How to Beat Waterfall Giant

Quick Strategy

Treat Waterfall Giant as two separate survival checks: kill the Giant before Steam Eruption grows out of control, then survive the explosion after the kill. Pressurize starts the Steam clock immediately, later actions keep increasing it, and the Giant gets a final About to Blow turn before Explode. Do not take lethal just because you can. Before finishing the Boss, know whether the next turn is covered by Block, Weak, Buffer, a defensive potion, or simply enough HP to absorb the explosion.

What This Fight Tests

Damage clock

Waterfall Giant keeps adding Steam Eruption as the fight continues and also has a healing turn. A deck that only blocks indefinitely eventually creates a post-kill explosion that becomes much harder to survive.

Turn-five defense

The first cycle reaches Pressure Gun on turn five, which is the main pre-kill damage spike. A deck that is comfortable against the earlier attacks can still lose a large amount of HP here if it spends too aggressively before the turn arrives.

Explosion answer

Reducing Waterfall Giant to zero HP is not the end of the fight. About to Blow gives you one final preparation turn before Explode, so your lethal line is only safe when you already know how that explosion will be handled.

Kill timing

Faster is generally safer because every extra cycle increases Steam Eruption, but rushing lethal without an explosion plan can still lose the run. The correct kill turn balances a smaller explosion against having the resources required to survive it.

Key Decisions

Lethal is not the same as safe lethal

Before I take the final damage line, I check the Steam Eruption number and the hand or resources available for the following turn. If killing now creates an explosion I cannot survive, I would rather use the current turn to improve the post-kill defensive line than treat zero Boss HP as an automatic win.

Weak is an explosion answer

The explosion may look like a special death effect, but Weak can still reduce the damage on that turn. That makes reliable Weak access unusually valuable because one correctly timed application can solve the largest single hit in the fight.

The Steam number determines how greedy you can be

Early Steam totals can often be absorbed with ordinary Block or HP. Once the number becomes very large, the deck needs a much denser answer. That is why damage scaling matters even for a defensive deck: killing earlier keeps the final defensive check inside a manageable range.

Resting before the Boss can be a real matchup decision

If the deck has excellent damage but a poor way to block one huge explosion, entering with more HP can be more valuable than another small upgrade. HP itself can be the planned resource that pays for the final hit.

Combat Data

Moves

8 moves

About to Blow

Stun
ABOUT_TO_BLOW

Explode

Special
EXPLODE
Enemy AI

Attack Pattern

Cycle

Pressurize → Stomp → Ram → Siphon → Pressure Gun → Pressure Up → repeat

Initial move: Pressurize
View pattern states
Pressurize
move
Next: STOMP_MOVE
Stomp
move
Next: RAM_MOVE
Ram
move
Next: SIPHON_MOVE
Siphon
move
Next: PRESSURE_GUN_MOVE
Pressure Gun
move
Next: PRESSURE_UP_MOVE
Pressure Up
move
Next: STOMP_MOVE
Explode
move
Next: EXPLODE_MOVE
About to Blow
move
Next: EXPLODE_MOVE
Must perform once
Fight Plan

Waterfall Giant 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

Pressurize and the first cycle

Start the damage clock immediately while keeping enough HP and defense for the turn-five pressure spike.

  • Use the opening Pressurize turn for setup or damage, but remember that it immediately adds 15 Steam Eruption. The final explosion clock has already started even though Waterfall Giant has not attacked yet.
  • Build damage scaling early enough that the fight does not become an endless defensive loop. Every later action continues adding Steam Eruption.
  • Track how much HP you are willing to spend before the explosion. Taking unnecessary chip damage early makes the eventual post-kill hit much harder to absorb.
Watch for
  • Treating the opening buff turn as unlimited setup time.
  • Building defense with no plan for how the Boss will actually die before Steam Eruption becomes too large.
Phase 02

First full cycle

Get through Stomp, Ram, Siphon, and Pressure Gun while pushing the Boss toward a kill before the Steam total becomes difficult to cover.

  • Account for Stomp applying Weak. If your damage turn depends heavily on Attacks, do not assume every part of the first cycle has the same offensive value.
  • Use the Siphon turn to pressure the Boss when possible. It is a Heal + Buff turn, so giving Waterfall Giant too much breathing room works against the damage clock twice: HP is recovered while Steam continues increasing.
  • Prepare for Pressure Gun on turn five instead of spending the previous hand as though the earlier smaller attacks define the whole fight.
Watch for
  • Allowing repeated healing and Steam growth because the deck feels defensively comfortable.
  • Entering the turn-five attack with no dense Block, Weak, potion, or HP buffer available.
Phase 03

Lethal and explosion

Kill Waterfall Giant while Steam Eruption is still survivable, then use About to Blow to prepare the exact answer for Explode.

  • Before dealing lethal damage, compare the current Steam Eruption total against the Block, Weak, Buffer, potion, and HP resources that can be available after the kill.
  • Use the About to Blow turn as a real preparation turn. Preserve or establish the defense required for Explode instead of treating the fight as finished.
  • If Weak is your explosion answer, make sure it is actually available for the explosion window rather than spending that access earlier on a smaller hit.
  • If the only realistic answer is HP, stop leaking unnecessary damage before lethal. Finishing with enough HP to tank the explosion is a valid plan.
Watch for
  • Taking lethal immediately because the Boss HP reaches zero without checking Steam Eruption.
  • Spending the About to Blow turn on irrelevant setup instead of preparing for Explode.

Dangerous Turns & Windows

Danger Window
Growing Steam Eruption

Pressurize adds 15 Steam Eruption immediately, and Stomp, Ram, Siphon, Pressure Gun, and Pressure Up each continue adding more. The post-kill damage therefore becomes harder to cover the longer the combat lasts.

Response: Treat damage scaling as part of the defensive plan. A faster kill does not only reduce incoming normal attacks; it also keeps the final explosion smaller.
Danger Window
Turn-five Pressure Gun

Pressure Gun is the main damage spike of the first cycle. The canonical damage data starts from 20 normally and 23 on Ascension before the fight moves into Pressure Up and repeats the attack cycle.

Response: Do not spend every defensive resource on the earlier smaller attacks. Enter turn five with a planned Block, Weak, potion, or HP line.
Danger Window
About to Blow

After lethal, Waterfall Giant does not disappear immediately. About to Blow must occur once before the Boss transitions into Explode.

Response: Use that extra turn deliberately. This is where you prepare Block, preserve Weak, use a defensive resource, or confirm that current HP is high enough to survive.
Danger Window
Explode

The explosion is based on accumulated Steam Eruption. A fight that has been allowed to continue too long can end with a 40, 50, or even 60-point defensive check after the Boss has already been reduced to zero HP.

Response: Keep Steam under control through damage scaling, then solve the remaining explosion with Block, Weak, Buffer, a defensive potion, or enough HP.
Before the Fight

How to Prepare for Waterfall Giant

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

DamageCritical

Can I kill before Steam Eruption becomes unreasonable?

Ready when

The deck has enough repeatable damage or scaling to move through Waterfall Giant’s healing and finish without allowing several unnecessary cycles of Steam growth.

Warning

Purely defensive decks can appear stable while quietly making the final explosion larger every turn.

Explosion defenseCritical

What is my answer after lethal?

Ready when

The deck has a realistic way to survive one large post-kill hit through Block, Weak, Buffer, potion support, or a sufficiently large HP pool.

Warning

A deck that can reduce Waterfall Giant to zero but cannot survive Explode has not actually solved the Boss.

Turn-five defenseHigh

Can I handle Pressure Gun before the kill?

Ready when

The deck can preserve a dense defensive answer or enough HP for the first cycle’s main attack spike instead of exhausting every resource on earlier turns.

Warning

The earlier attacks can make the matchup look safer than the turn-five pressure actually is.

WeakHigh

Can I line up Weak with the explosion?

Ready when

A reliable Weak source can be retained, redrawn, generated, or otherwise made available for the final explosion window.

Warning

Weak has much more value on the explosion than on a small ordinary attack, so using the only application too early can waste the matchup-specific value.

HPHigh

Can I simply survive the remaining explosion?

Ready when

Current HP is high enough that the expected explosion can be absorbed after accounting for the damage likely to be taken during the normal cycle.

Warning

Entering the fight low because the deck normally blocks well is risky when the final hit may demand a large amount of HP all at once.

PotionMedium

Do I have a one-turn answer reserved?

Ready when

A Block potion, Weak potion, Lucky Tonic, or another defensive potion has a defined job on Pressure Gun or the final explosion rather than being spent casually earlier.

Warning

Waterfall Giant is exactly the kind of matchup where one defensive potion can convert an otherwise losing single turn into a win.

Character Matchups

Waterfall Giant 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 can struggle more with the final explosion when the deck is built around damage rather than dense Block. The practical answers are usually to kill Waterfall Giant fast enough that Steam stays low, enter with enough HP to absorb the explosion, or reserve a specific defensive resource for the final turn. Vulnerable-dependent finishers also need careful timing because the post-kill explosion still has to be survived after the damage turn is over.

Prioritize
  • Push damage early enough that Steam Eruption does not grow into an unrealistic Block requirement.
  • Rest before the Boss when HP is the most reliable way the current deck can pay for the explosion.
  • Reserve a Block, Weak, or defensive potion line when raw HP alone is not enough.
  • If a large finisher depends on Vulnerable, make sure that setup does not consume the same resources needed to survive after lethal.
Watch for
  • Building a high-damage deck and assuming killing the Boss immediately ends combat.
  • Entering low HP because ordinary turns are easy to Block while having no answer to one very large post-kill hit.

Silent benefits from being able to preserve a defensive answer for exactly the turn that matters. Retaining a Weak source is particularly strong against Waterfall Giant because the explosion is the matchup’s main single-hit check, so Weak has far more value there than on one of the earlier smaller attacks.

Prioritize
  • Preserve Weak for the explosion when the deck has a reliable way to retain or recover it.
  • Do not spend the only dense defensive answer merely to perfect-block a smaller early attack.
  • Keep enough damage scaling that Steam Eruption does not continue growing while the deck waits for a perfect defensive setup.
  • Use the About to Blow turn to finish assembling the explosion answer instead of treating lethal as the end of combat.
Watch for
  • Using Weak early because it saves a small amount of HP and then lacking it for the much larger explosion.
  • Playing too slowly simply because Silent can repeatedly defend the normal attack cycle.

Necrobinder is naturally well positioned for Waterfall Giant when the defensive shell is functioning. Strong Block access can cover very large explosion turns, while the character’s natural damage progression reduces the need to over-draft extra scaling specifically for this Boss. Reliable Weak access can make the final defensive check even easier.

Prioritize
  • Trust an already functional defensive shell instead of warping the whole deck around the explosion.
  • Preserve reliable Weak access for Explode when that reduces the final hit more efficiently than another ordinary Block card.
  • Keep the damage engine moving so Waterfall Giant does not receive unnecessary extra Steam cycles.
  • Judge whether resting is actually necessary from the Block plan rather than automatically entering every Boss at maximum HP.
Watch for
  • Over-drafting damage scaling when the existing engine already outpaces Waterfall Giant.
  • Assuming strong Block means Steam Eruption can be allowed to grow forever.
Failure Analysis

Common Waterfall Giant Mistakes

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

01

Thinking lethal ends the fight

You use every remaining resource to reduce Waterfall Giant to zero HP and assume combat is finished.

Why it fails

Waterfall Giant enters About to Blow before Explode. If the Steam Eruption total is larger than the defense or HP you can produce afterward, the run can die after you have already dealt lethal.

Better decision

Before taking lethal, calculate the post-kill turn. Keep the Block, Weak, potion, Buffer, or HP required to survive Explode.

02

Blocking forever because the normal attacks look manageable

The deck comfortably handles Stomp and Ram, so you keep extending the fight without improving damage.

Why it fails

Steam Eruption continues rising and Siphon allows the Giant to heal. The normal cycle can remain manageable while the eventual explosion becomes impossible.

Better decision

Treat damage scaling as defensive value. End the fight while the Steam total is still inside the range your deck can cover.

03

Forgetting the turn-five pressure spike

You spend HP, Block, or potions freely on the first few attacks because none of them look especially threatening.

Why it fails

Pressure Gun arrives on turn five and is the main pre-kill hit of the first cycle. A deck that reaches it depleted can lose the HP that was supposed to absorb the final explosion.

Better decision

Plan the first cycle backward from Pressure Gun. Preserve one dense defensive line for that turn.

04

Using Weak on the wrong attack

You spend the only reliable Weak application on an ordinary attack because it saves some immediate HP.

Why it fails

The explosion is often the largest single attack in the matchup, so the same Weak application can prevent far more damage if it is available at the end.

Better decision

When Weak access is limited, reserve or recover it for Explode unless using it earlier is necessary to survive.

05

Skipping a rest when HP is the actual explosion plan

You take an upgrade because the deck is strong and assume more power is always better before the Boss.

Why it fails

Some decks, especially ones without reliable dense Block, solve Waterfall Giant most cleanly by entering with enough HP to absorb the final hit. A small upgrade may contribute less than the health required to survive.

Better decision

Before choosing the campfire action, ask what actually covers Explode. If the answer is HP, resting is part of the Boss strategy rather than a sign that the deck is weak.

Entity Relationships

Appears In

1 encounter

Waterfall Giant

Boss
Act 1 - Underdocks →
Game ID: WATERFALL_GIANT Data version: v0.107.1 · Main Type: Boss