Slay the Spire 2 High Ascension Guide: Strategies for A5 Through A10

What Changes at High Ascension

Every Ascension level stacks a permanent modifier on top of all previous ones. By A10 you’re playing a fundamentally different game than A0. The enemies are tougher, you have fewer resources, and the decisions that carried you through low Ascension will get you killed.

Here’s every modifier so you know exactly what you’re dealing with.

A1 — Swarming Elites: More elite encounters appear on the map. You’ll face more dangerous fights per act.

A2 — Weary Traveler: Rest sites heal 25% of max HP instead of 30%. Your safety net is smaller.

A3 — Poverty: You earn 25% less gold. Shops become luxuries, not givens.

A4 — Tight Belt: One fewer potion slot. Less emergency healing, less burst.

A5 — Ascender’s Bane: You start every run with a Curse card in your deck. This is the first major wall most players hit.

A6 — Inflation: Card removal starts at 100 gold (up from 75) and goes up 50 gold per removal instead of 25. Trimming your deck gets expensive fast.

A7 — Scarcity: Rare cards and upgraded cards appear half as often in rewards. Your card pool is weaker on average.

A8 — Fortified Foes: All enemies have more HP. Fights last longer. You take more total damage.

A9 — Empowered Foes: All enemies deal more damage. Every turn of every fight is more dangerous.

A10 — Double Boss + Ascender’s Bane: Act 3 ends with two boss fights back to back, and you start with Ascender’s Bane again (stacks with A5, so yes, you have two Curses at A10 if both apply).

A5: The Ascender’s Bane Wall

Most players plateau here. Ascender’s Bane is an unplayable Curse that’s Eternal — you cannot remove it from your deck. It sits there, clogging your draws forever.

What actually works:

Draft extra draw. Every extra card drawn dilutes the Bane’s impact. If you draw 6 cards instead of 5, the Bane is taking up 16% of your hand instead of 20%. That math matters over a full run.
Exhaust is your friend. Cards that exhaust other cards can sometimes target Ascender’s Bane depending on the wording. Check which exhaust tools work on Curses for your character.
Path around elites in Act 1. With A1’s extra elites already on the board, taking early elite fights while your deck still has a dead card is risky. Go for standard fights and events first, get some pieces, then tackle elites in mid-Act 1 or Act 2.
Don’t panic-pick. The urge to grab any card that seems good to “dilute” the Curse is real but wrong. A lean 13-card deck with one Curse is better than a bloated 20-card deck with one Curse. Percentage-wise, the lean deck actually draws the Curse more often, but every other draw is higher quality.

A6-A7: The Resource Crunch

These two levels squeeze your economy and card quality at the same time.

A6 Inflation strategy: Card removal is now a major investment. Be selective about what you remove. In A0-A5, removing Strikes early was almost automatic. At A6+, that 100g (and 150g for the second removal) might be better spent on a relic or a key card from the shop. Evaluate each removal against what else you could buy.

A7 Scarcity strategy: With rare cards appearing less often, you can’t rely on finding your build’s payoff card. Build around commons and uncommons that work well together. Rares are bonuses, not foundations. This changes character evaluation too — characters whose core strategies use common/uncommon cards (like Ironclad exhaust) handle A7 better than characters who need specific rares to come online.

A8-A9: The Damage Race

Enemies have more HP (A8) and hit harder (A9). Combined, this means every fight is both longer and more punishing per turn. You take more total damage per run, and you have less room to recover.

What changes in practice:

Block thresholds shift. The amount of Block that used to fully cover a turn doesn’t anymore. If enemies hit 5 damage harder at A9 and you were barely covering their damage before, you’re now eating 5 chip damage every turn. Over a 4-turn fight, that’s 20 HP lost. Across an act, it adds up to death.
Damage per energy matters more. At A8, inefficient attacks mean the fight drags another turn, which means another turn of taking hits. Cards that deal 4 damage for 1 energy were fine at A0. At A8, you need 6-8+ damage per energy or the math doesn’t work.
Potions are for elites and bosses only. With A4’s reduced potion slots already in effect, you can’t afford to use potions on hallway fights. Save them for the encounters that actually threaten your run.

Specific adjustments:

Take Vulnerable applicators higher. Making enemies take 50% more damage shortens fights significantly, which means less total damage taken.
Block cards need to provide 8+ Block to be worth playing. Below that, you’re spending energy to not quite survive.
AoE becomes critical. Multi-enemy fights at A8-A9 are the most common run-enders because you can’t kill the back row fast enough and they grind you down.

A10: The Double Boss

Two bosses in Act 3. Back to back. Your deck has to handle both, and you don’t get to rest or shop between them.

The fundamental shift: Your deck can’t be one-dimensional anymore. A deck that perfectly counters one boss might get destroyed by the other. You need versatility. Enough single-target damage for bosses with big HP pools, enough Block for bosses with high damage turns, and enough flexibility to handle whatever the second boss throws at you after you’ve already spent resources on the first.

Doormaker, the community’s most controversial boss, can appear as one of your two fights. Building a deck that handles Doormaker plus one other random boss is a real deckbuilding challenge. There’s no universal answer here. You have to evaluate what your deck can handle and sometimes accept that a specific boss pairing will end your run.

Practical tips for double boss:

Save at least one potion for the second fight. Ideally two.
Your deck should be able to win without drawing perfectly. Consistency beats peak power at A10 because you need to win twice, not once.
Rest before the boss floor if your HP is below 60%. You cannot afford to enter the first fight wounded.

General High Ascension Principles

These apply from A5 onward and get more important as you climb.

Take less optional damage. Every ? event that costs HP is worse at high Ascension. Every elite fight you didn’t need to take is a risk that doesn’t always pay off. Calculate whether you can actually afford the HP loss before you commit.

Draft for the fights ahead, not the fights behind. If you just beat an elite and your deck feels strong, don’t coast. Look at the upcoming map. Is there another elite? A boss in two floors? Draft for what’s coming.

Upgrade Block cards. At low Ascension, upgrading attacks feels better because the fight ends faster. At high Ascension, the upgrade from 5 Block to 8 Block on a defensive card is often more valuable because it’s the difference between surviving and not.

Learn enemy patterns. Every enemy in Slay the Spire 2 follows a set attack pattern. At high Ascension, knowing that an enemy will attack for 18 damage on turn 2 lets you plan your Block spending. You can’t afford to guess anymore.

This is a game where knowledge compounds. Every A10 win teaches you something that makes the next attempt more informed. The climb is supposed to be hard.