You finally beat the Heart. You’re feeling like a tactical genius. Then, you see that little toggle at the bottom of the character select screen. Ascension 1. You click it. It feels fine at first—more elites just means more relics, right? But then you hit the wall. Somewhere around Ascension 10 or 17, the game stops being a fun deck-builder and starts feeling like a personal vendetta held by a math equation.
Slay the Spire ascension levels aren't just "hard modes." They are a fundamental redesign of how the game's economy and mechanics function. If you try to play A20 the same way you play A0, you will lose. Every single time. Honestly, the jump from A16 to A17 alone ruins more runs than the Awakened One ever could.
Most players treat these levels as a linear difficulty curve. That’s a mistake. It’s more of a staircase where some steps are covered in grease and others are missing entirely. To climb, you have to stop looking for "the perfect build" and start looking for "the least bad way to survive the next floor."
The Brutal Reality of the Ascension Climb
Look, the first few levels are actually a gift. A1 increases Elite spawn rates. If you’re good at the game, A1 is easier than A0 because more Elites equal more Rare cards and more relics. You get stronger faster.
But then the game starts taking things away.
At A5, you no longer heal to full after a boss. Suddenly, that "chip damage" you took from a Louse in Act 1 matters in Act 2. By the time you hit A10, you’re starting every run with a Parasite (Ascender’s Bane) in your deck. It’s a curse that can’t be removed. It’s there to ruin your opening hand draw, and it never goes away. It fundamentally changes how you value card draw and deck thinness.
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The real nightmare begins at A17. This is where the enemy AI and move sets change. It’s not just that they have more HP or hit harder. They get meaner. The Gremlin Nob applies more Vulnerable. The Chosen puts more Dazes in your deck. The multi-attacks from Birds or the Book of Stabbing become exponentially more lethal because every single hit scales with the increased damage buffs.
Why Your "Go-To" Strategy Fails at High Levels
On lower levels, you can force an archetype. You see a Noxious Fumes and think, "Okay, I'm a poison deck now." You spend the rest of the run hunting for Catalyst and Burst. On A15+, forcing a deck is a death sentence.
The game is about solving immediate problems. Can you beat Nob? If not, take that shitty Carnage or Wild Strike even if it ruins your "synergy" later. You have to survive Act 1 first.
Many players underestimate the impact of Ascension 17-19.
- A17: Normal enemies become terrifying.
- A18: Elites get upgraded moves (the Slavers' wound generation is disgusting).
- A19: Bosses become absolute units.
- A20: You have to fight two Act 3 bosses back-to-back.
Think about that. You spend the whole game tailoring your deck to beat Time Eater, only to realize you have to fight the Awakened One immediately afterward with whatever health you have left. It forces you to build a deck that is "good at everything" rather than "perfect at one thing."
Mastering the Micro-Decisions
Survival in Slay the Spire ascension levels comes down to the math of "Effective HP." Every point of health is a resource you spend to get stronger. If you finish a fight with 50/70 HP, you didn't just "win." You spent 20 HP. Was the reward worth it?
The Shop and the Path
Stop buying shiny Rare cards just because they look cool. At high Ascension, the most valuable things in the shop are often:
- Removing a Strike. Strikes are terrible. They are the reason you die.
- A Potion. A well-timed Fire Potion or Cultist Potion saves you 30+ HP in an Elite fight.
- A Key Relic. Something like a Kunai or Shuriken that defines your scaling.
Pathing also changes. On A0, you might dodge Elites because you’re scared. On A20, you must hunt Elites in Act 1 to get the relics necessary to survive Act 2. If you enter Act 2 without at least two or three solid relics, the Avocado (Shelled Parasite) will simply end your run on floor 18. It’s brutal, but it’s the truth.
The "Card Draw" Fallacy
People love "infinite" decks. They want to play 50 cards a turn. On A19 and A20, the Time Eater and the Corrupt Heart exist specifically to kill you for doing that. You need "impact per card."
If you're playing the Silent, a Blade Dance is great, but without an Accuracy or a Shuriken, you're just proc-ing the Heart’s Beat of Death for no reason. You have to weigh the value of every single click. Is playing this Defend worth the energy, or should I just take the 5 damage and play a Power that helps me win in three turns? Usually, at high Ascension, the answer is "Take the damage, play the Power." You have to end fights fast.
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Breaking Down the Character-Specific Hurdles
Each character handles the climb differently. The Ironclad can usually brute-force his way through Act 1 thanks to Burning Blood, but he struggles with scaling in Act 3. The Defect is the opposite; if you survive the first ten floors, your Orbs might carry you, but getting those Orbs online while a Sentries fight is screaming at you is a nightmare.
The Ironclad: Exhaust is Not Your Enemy
New players hate exhausting cards. "Why would I want my cards to disappear?" they ask. Because your deck is full of garbage. Feel No Pain and Dark Embrace turn the Ironclad into a god. At A20, an Ironclad deck that doesn't utilize the Exhaust pile is almost certainly going to fail. You need to thin your deck during the fight to get to your heavy hitters like Bludgeon or Feed.
The Silent: The Shiv vs. Poison Trap
Shivs are fun. Poison is reliable. At A17+, the Silent needs Wraith Form. Honestly, Wraith Form is arguably the best card in the game. Intangible is the only way to survive the 60-damage hits coming from the Heart or the Automaton. If you see it, take it. Don't worry about the Dexterity loss; the fight should be over by the time that matters.
The Defect: Focus or Bust
The Defect lives and dies by Focus. If you don't find a Defragment, a Biased Cognition, or at least a Data Disk, your Orbs are just fancy light shows that do 3 damage. At high Ascension levels, the Defect is the most "RNG dependent" character because his starter deck is objectively the weakest for dealing with Act 1 Elites. You have to gamble on finding a Glacier or a Cold Snap early.
The Watcher: The Math Queen
The Watcher is technically the strongest character, but she’s the hardest to play at A20. One wrong turn in Wrath stance and you’re taking double damage from a boss. You're dead. You have to calculate exactly when to enter Calm and when to stay in Divinity. It’s basically doing homework while a Gremlin Wizard counts down to your demise.
Actionable Steps to Beat A20
If you're stuck on a specific level, stop doing the same thing. Change your heuristic.
- Skip more cards. You don't have to take a card every time you win a fight. A 35-card deck is usually worse than a 22-card deck. If the cards don't solve a problem you currently have (e.g., "I need AOE for Slime Boss"), hit skip.
- Value Potions higher. Take the Alchemize. Buy the potion in the shop. They are "get out of jail free" cards for when the RNG gives you a hand full of five Strikes.
- Learn enemy patterns. You should know that the Gremlin Nob will use Bellow on turn 1 and then attack. You should know the Champ will cleanse his debuffs at 50% HP. If you don't know these patterns, you're playing blindfolded.
- Evaluate your relics. If you get a Coffee Dripper, take it. Not being able to rest is scary, but having 4 Energy every turn means you take less damage, which means you don't need to rest.
- Watch the pros. Spend an hour watching Lifecoach or Baalorlord. They explain why they take a "bad" card in a specific situation. It’s eye-opening.
The climb through Slay the Spire ascension levels is meant to be a grind. It’s a lesson in humility. You’ll have a deck that feels invincible, only to get crushed by a bad draw against the Spear and Shield. That’s the game.
Accept that some seeds are just harder than others. Your job isn't to win every run—even the best players in the world don't have a 100% win rate on A20. Your job is to make the best possible decision at every single node. Do that, and the wins will start coming. Eventually. Sorta.
Next Steps for Your Climb:
Check your recent run history. Look at your deaths. If you are dying in Act 2 consistently, you aren't picking enough high-damage cards in Act 1. If you're dying to the Heart, you're lacking "scaling" (ways to get stronger as the fight goes on). Focus on fixing that one specific phase of the game in your next five runs. Stop worrying about the win and start worrying about the "Solve."