If you are trying to figure out how to start the Fake Merchant boss fight in Slay the Spire 2, the short answer is simple: you need to get a Foul Potion, hold onto it, and use it on The Merchant??? event instead of a real Merchant. The hard part is not the fight itself. The hard part is putting the pieces together in a game that clearly wants this secret to feel half rumor, half punchline.
That is why so many players miss it.
How to Trigger the Fake Merchant Fight in Slay the Spire 2
On the surface, Slay the Spire 2 trains you to think about potions and merchants in straightforward, practical terms. Potions are combat tools. Merchants are places to spend gold, remove cards, and stabilize shaky runs. The Fake Merchant encounter disrupts that logic. It asks you to carry a highly specific event potion across multiple floors, ignore a perfectly reasonable short-term payoff, and then recognize that one seemingly odd shopkeeper is not actually a normal shopkeeper at all.
Here is the full chain:
- Encounter the Potion Courier event
- Choose the Foul Potions instead of the random Uncommon potion
- Carry at least one Foul Potion until you find The Merchant???
- Throw the Foul Potion at the Fake Merchant instead of shopping
That is the trigger. The fake merchant drops the act, becomes hostile, and the event turns into a secret combat encounter against the impostor. The "boss fight" is less about hidden execution and more about hidden preparation. If you know the recipe, it is straightforward. If you do not, it is exactly the sort of interaction you might never discover organically.
Where to Get a Foul Potion
First, you need the Potion Courier event. That event can reward you with three Foul Potions instead of a random Uncommon potion. This is the real setup step, and it is the one that determines whether the rest of the secret is even possible. If you skip the Foul Potions, the run is effectively over as far as this encounter is concerned. The game does not present the choice as some giant neon arrow pointing toward a hidden boss. It just gives you a weird item with a weird description.
And that description is the clue.
A Foul Potion deals damage in combat, but it also has a special line: it can be thrown at the Merchant for 100 gold instead. That alone is already one of the strangest item interactions in the game. Newer players understandably interpret that line as the full gimmick. They see the potion, think "nice little merchant trick," cash it in at the next normal shop, and move on. That is a completely rational choice. It is also the exact choice that locks them out of the Fake Merchant fight.
How to Recognize the Fake Merchant
To trigger the secret encounter, you need to save at least one Foul Potion long enough to find The Merchant???, the counterfeit merchant event. Current game data and public reporting both point to this as a rare late-run event, which is one reason the fight feels so elusive in practice. You are not just looking for one specific random event. You are looking for the overlap between two specific random events, while also preserving a potion slot for long enough to capitalize on it.
That overlap is the real challenge.
Once you finally find The Merchant???, the last step is easy: throw the Foul Potion at the Fake Merchant instead of treating the room like a normal shopping stop. The impostor reveals itself, and the secret fight begins.
What Happens If You Use a Foul Potion on a Real Merchant?
If you throw a Foul Potion at a regular Merchant, you simply receive 100 gold. That is the "safe" use. It is decent value and a perfectly valid play, but it locks you out of the far more lucrative Fake Merchant encounter. The game does not punish you for using it early — it just closes the door to the secret.
Is the Fake Merchant Fight Worth It?
For new and intermediate players, there is a practical question underneath the novelty: is this actually worth doing? In most cases, yes. Public documentation and gameplay footage indicate that beating the Fake Merchant rewards you with a substantial payout, including 300 gold and the fake relic stock you did not purchase. That matters because the normal "safe" use of a Foul Potion at a real Merchant only gives you 100 gold. From a pure value perspective, the secret fight has a much higher ceiling.
But there is a tradeoff, and it is an important one. Carrying a Foul Potion for multiple acts is not free. Potion slots are valuable. Potions in Slay the Spire 2 often represent emergency tempo, elite insurance, or boss stabilization. Holding a Foul Potion in reserve means accepting an opportunity cost — you are effectively reserving one slot for a future high-roll event instead of using every consumable resource to win the run immediately in front of you.
That is why the best advice is not "always do this." The best advice is "do this when your run can afford the greed." If your deck is stable, your HP is healthy, and you can reasonably hold a potion without sabotaging your next few combats, the Fake Merchant setup is one of the coolest secrets in the game. If your run is barely holding together, preserving a novelty trigger may be less important than using your resources to survive. The secret is lucrative, but dead players do not cash out.
This is also why the encounter is such a good piece of roguelike design. It rewards memory, restraint, and curiosity all at once. You have to remember what the potion does, resist the urge to spend it for immediate gold, and be curious enough to test an unusual interaction when the moment finally appears. The game is asking whether you are willing to trust that a strange item might have a stranger payoff.
Final Verdict
The Fake Merchant fight is one of Slay the Spire 2's best secrets because it rewards patience and game knowledge instead of blind luck alone. The fake merchant plays with one of the safest assumptions in the genre — that a shop is a refuge — and twists it into something theatrical. It looks like a commercial break in the run. In reality, it is an ambush waiting for a player who understands the joke.
Final verdict: To start the Fake Merchant boss fight, take Foul Potions from the Potion Courier event, keep one until you find The Merchant???, and throw the potion at the fake shopkeeper. If your run can spare the potion slot, it is absolutely worth setting up. Just do not mistake "secret" for "free." The real cost is everything you give up while waiting for the moment to appear.
For more event breakdowns, visit our Events Database. For relic and potion interactions, check the Relic Database.