How Many Acts in Slay the Spire?

A quick breakdown of each act in Slay the Spire.

by Yaroslav Mokliak
UPDATED: Mar 18, 2026

Slay the Spire is split into 4 acts. Three of them make up the normal run, and the fourth one sits quietly at the end as a hidden final challenge. Most runs go through the first three acts only, where the game gradually ramps up the difficulty.

Every act introduces tougher enemies and nastier elites. What felt manageable earlier suddenly hits harder a few floors later. That’s just how the climb works, the deeper you go, the less forgiving things become.

Moving forward is simple enough: beat the boss at the end of an act and the next area opens. Act 4 works a little differently, though. To unlock it during a run, you need to collect three special keys along the way.

Below is a breakdown of each act in Slay the Spire.

Act 1: The Exordium

You start the game in the Act 1 – the Exordium. It is a dark, mysterious ruin filled with early-game enemies. The enemies in Act 1 are relatively easy compared to later acts. Common enemies include Jaw Worms, Slimes, and Cultists.

The boss for Act 1 is randomly selected from one of three possible bosses:

The Guardian: A defensive automaton that alternates between offensive and defensive phases.
Hexaghost: A ghostly entity that grows stronger as its health decreases.
Slime Boss: A large slime that splits into two smaller slimes when damaged.

Act 2: The City

The City is the next act, which is available after you beat the boss from the first Act. It is a bustling city, that introduces more difficult enemies with varied strategies. You’ll face Snecko (which causes confusion and randomizes card costs), Bandits, and Chosen, among others.

The Act 2 bosses are tougher:

The Collector: A summoner that calls minions to aid in battle.
The Bronze Automaton: A mechanical warrior with minions that can steal your buffs.
The Champ: A gladiator-type enemy that gains strength and adapts throughout the fight.

Act 3: The Beyond

Act 3 (The Beyond) is the second location, which is available after you defeat the boss from Act 2. The Beyond is a more otherworldly and surreal landscape with twisted creatures.

The enemies in here are varied and often have unpredictable abilities, such as Darklings (which revive after being killed), Reptomancers (which summon daggers), and Transient (which have a countdown before disappearing).

The Act 3 bosses are:

The Time Eater: A powerful foe that limits how many cards you can play each turn by ending your turn after playing 12 cards.
Donu and Deca: Two bosses that complement each other by buffing their strength and defense as the fight progresses.
The Awakened One: A boss with two phases, the second phase occurs after defeating the first form.

Act 4: The Ending (Hidden Act)

The Ending is the last act, a mysterious final level. Here you will see only one path, which contains of 3 locations – the shop, the miniboss, and the final boss.

The miniboss (or better bosses), The Shield and Spear, a unique boss bosses who work in tandem, making for a tricky encounter.

The final boss is The Heart of the Spire. This is the true final boss of the game. After defeating the final boss you’ll see a short comic, unique for each character.

How to Unlock Act 4

At first it seems like Slay the Spire ends after Act 3. You defeat the boss, the run finishes, and that’s it. A lot of players assume that’s the whole game. But there’s actually one more act hidden behind a small requirement the game doesn’t really highlight.

First, you need to win a run with the four original characters:

After that, future runs start including three special keys. To unlock Act 4, you must collect all of them in the same run.

Ruby Key — taken at a campfire by choosing Recall.
Emerald Key — dropped by a stronger elite enemy marked with a green flame icon.
Sapphire Key — found in a treasure chest, but you have to give up the relic inside.

If you manage to grab all three keys and defeat the Act 3 boss, a new path opens instead of the usual ending - Act 4.

Conclusion

So, there are 4 acts in Slay the Spire in total. The first 3 acts are available from the very beginning, and the last one is unlockable by collecting 3 Keys during the run.

Each act is harder than the previous one and has the final boss to defeat.

Yaroslav Mokliak

CEO | Editor | Content Writer

With over 15 years of playing games and 5 years of writing articles, Yaroslav is a CEO and content creator at HermitGamer. Yaroslav regularly plays video games, creates useful guides, and writes reviews with his opinion on new and old titles. His main goal is to make HermitGamer a platform, where each gamer can find the answers.