Slay the Spire – The Nine Bosses

Other Slay the Spire Guides:


The Guardian has a kind heart beneath his fierce exterior. He often visits animal shelters and adopts cats and dogs, though this habit is becoming unsustainable. He donates gold from the corpses of spire-climbers to the RSPCA.

He has two forms, “standing” and “shell”. He begins in standing and switches to shell after taking 30 unblocked damage. When switching to shell, he gains 20 block immediately (and his queued action is interrupted), but doesn’t gain the 3 thorns damage until his own turn. Choose your attacks in the right order to be able to do the most damage before the block comes up if you can’t break through it.

Each time he goes back into standing form, it takes 10 damage more to get him into shell than the last time. Each time except the first, he does a 5×4 whirlwind attack, then blocks on the next turn, then does a 32 damage attack, then goes for a debuff. You ideally want to make him switch forms before the 32 damage attack.

During shell form, even though the thorns will damage you for attacking, you want to be aggressive. This is because this damage doesn’t count towards making him switch forms, so you won’t have to fight the standing form as many times if you can hurt him in shell form. Whenever he does the x2 attack while in shell form (usually 8×2), it means he is about to change forms.

Slime Boss

The Slime Boss was part of a turbulent social group during high school where she was constantly scheming and gossiping to try to become the queen of her group. She fell out with her friends after graduation, who were glad to be rid of “that two-faced drama queen”. She has become lonely and has turned to online dating and fighting spire-climbers to meet new people.

In her initial form she cycles between three attacks – 9 damage and adds 3 Slimed cards to your deck, then nothing (a charge up move), then a strong attack which I think is 35 damage. Reducing any slime form to half health will interrupt its queued action, and cause it to split into two smaller slimes each with whatever health the bigger one was on at the time.

There are two ways to time your attacks that reduce to half health:

  • Use them to interrupt an attack that you don’t want to deal with, or 
  • Keep the slime just above half health on a previous turn, then do as much damage as you can on the next turn so the two smaller slimes will have less health. 

Be aware of effects that damage the slimes at the start of their own turn, like poison, since these can also cause the slime to split that turn. But effects that damage the slime after attacking, like thorns, will not. Also note that if you completely kill a slime, it won’t split.

The grey medium and small slimes apply Frail while the green slimes apply Weakened. The medium ones apply for 2 turns and the small ones apply for 1 turn. Also, the attacks of the medium slimes give 2 Slimed cards and the small give 1 Slimed card. It’s usually better to kill the green slimes first unless you’re a poison deck.

Note that when a slime splits it loses all debuffs like weak, poison, reduced strength etc.

This is a difficult fight with lots of choices to make (do you pay to exhaust the slime cards, attack the enemies to finish the fight faster, or defend to take less damage?) You don’t want to drag it out too long, and you will probably use potions to help you at key moments like when splitting a slime.


Hexaghost was a math teacher who died from job-related stress after too many years of trying to get unruly students to listen and learn. In his free time he enjoyed playing card games, a hobby which he has been able to keep up in his afterlife thanks to digital card games and ghost-machine interfaces. Hexaghost’s favorite number is 6.

After each action, Hexaghost lights up one of his corners. Once all six are lit, he performs a multi-attack that also adds three Burn+ cards to your deck which do 4 damage instead of 2. His regular attacks can also add burn cards to your deck. Be aware that you can block the damage of burn cards in your hand by playing defence cards.

Reducing his strength with Disarm or Malaise will make the multi attacks easier to block. If you don’t have a way to block the multi attacks, try to keep your health above 36 going into that turn.

Although you don’t want to take too much incidental damage in this fight, it’s important to be aggressive and kill him quickly before your deck gets clogged with too many burn cards that stop you from drawing good hands.

Bronze Automaton

The Bronze Automaton has a keen interest in time travel and politics. He enjoys posing hypothetical questions to his minions like “if you could go back in time to the 2012 elections, would you vote for Mitt Romney on the chance that it prevents Trump 2016?” (His minions are Democrat voters). He writes to his congressmen from his floor in the spire and urges them to grant more stacks of the artifact buff to their citizens.

His two minions use a move in their first few turns that takes a card out of your deck, and it always seems to get one of your best cards, though I’m not sure exactly how they decide. The minions don’t respawn, so you usually want to kill them first to avoid taking more damage and to get your cards back. When you get your card back, it goes into your hand and can be cast that turn.

After about 6 turns or so, the Automaton will use a hyper beam attack which does massive damage and then stuns him on his next turn. Because of the artifact stacks and high health total, you probably won’t be able to kill the automaton before his first hyper beam. I think that the Automaton always uses block and gain strength on the turn before the hyper beam, so if you anticipate that the beam is coming next turn, you can try to stack the top of your deck with defence cards or retain them in your hand (with Headbutt / Warcry or Well Laid Plans). Otherwise you will need to use potions – be aware that weak poitons are blocked by the artifact buff – or just have a high enough life total to survive.

Apart from the hyper beam, it’s also possible to die in the following turns to multi attacks since he has increased his strength. Or, you might let him live long enough to cast a second hyper beam and die to that. But apart from these dangers, this is a pretty straightforward fight.


The Collector prefers to be called “The Hoarder”. Apart from hoarding her torch head minions, she also hoards relics from fallen spire-climbers and uses these to create massive artworks that make the rooms in her house look like famous tourist destinations from around the world, including a pyramid of Giza made entirely from Runic Pyramids. She hopes that new bosses get added to the spire soon so that she can take some time off and see these tourist destinations in person.

Whether or not the Collector will summon more minions after her initial summon is random. It’s possible that if you kill them, you might just have several turns in a row where you get to fight her alone. But it’s also possible she resummons them and you spend a lot of energy fighting minions instead of fighting the main boss.

If you have a very aggressive deck, you might be able to kill her quickly because she has lower health than other bosses on this map. Otherwise, you should note that she increases the strength of her minions at the same time as she increases her own strength. This means you will want to clear out the minions from time to time just to reset their strength to zero even if she does resummon them.

This is probably the most dangerous fight on this map, especially when you get attacked by a x3 attack from the Collector while being attacked by two minions at the same time (minions always attack). She can also use a debuff that applies multiple debuffs at once, so an artifact potion or a Panacea will only prevent the first one that is applied.


The Champ is a sociology professor who studies toxic masculinity. He decided to adopt a hypermasculine persona as part of an experiment, but after a while he couldn’t tell the difference between that persona and his original self. His colleagues tried to snap him out of it, but he insisted that he was still the same person inside and that it was all under control. He refused their help and moved to the spire ostensibly to continue his experiment in peace, though as the bodies of spire-climbers piled up, his colleagues became more certain that the experiment would never end.

The Champ has two forms. When he is reduced to half health, his next action will be to apply a buff that clears all debuffs and gives him 6 strength. However, unlike slimes and some other enemies, reducing him to half health doesn’t interrupt his current action.

In his first form he uses a mixture of attacks, buffs, and debuffs, including a Metallicize buff that gives him 5 armor each turn (and a bit of extra armor the turn he casts it). Metallicize stacks with previous casts, so if you let him use it too often, he might get to a point where he is impossible to kill. If you don’t have any attacks that get stronger over time, you’ll need to get him into his second form before he uses it too many times.

In his second form he uses some normal attacks and some x3 attacks which can do massive damage like 19×3 (depending how much strength he has) so you don’t want to leave him in this form for too long. I think he can also apply Vulnerable to you which you can prevent with an artifact potion. (It’s not as good to use artifact potions in the first form because he applies multiple debuffs at once).

You might try to keep him just above half health until you can do big damage over the next two turns, so that he won’t have much health left when he starts attacking in his second form. Noxious Fumes decks without Catalyst might struggle to kill this boss, because he clears poison when changing forms and it would take a while to reapply it.

Time Eater

I have lots of interesting things to say about the Time Eater, but I have to be quick because she could make me end this paragraph at any moment.

The Time Eater is the easiest third floor boss for a lot of decks. She doesn’t attack every turn, and she only gains strength after you have played 12 cards, so you have some control over when it happens. If you have a deck that scales up like Noxious Fumes, Demon Form etc. then you can just play those cards, ignore all card drawing cards and small attacks, and only play the defences you need to survive. This will allow you to become very strong without letting the Time Eater become strong.

Keep watch of the counter that goes up to 12. You usually don’t want to be only allowed to play 1 card before your turn is automatically ended. Note that once it hits 12, you don’t even have a chance to take other actions like drinking potions, so do this before playing your 12th card. Try to anticipate when you’re going to hit the 12 from a turn in advance. Have a look at your draw pile and think about how many cards you will want to play next turn. You might play a 9th card even if you don’t need it if you think you can only play three next turn, just like you might play a 12th you don’t need so the turn after you can play as many as you want (up to 12).

At half health, she heals herself and removes debuffs. This is annoying, but shouldn’t affect your strategy. It doesn’t interrupt her, and it takes a turn to cast, so it’s possible to kill her in one go with some decks.

Infinite combo decks don’t work against the Time Eater. Even though you can still use your combo for 12 cards each turn, this would make her strength go up too fast so you probably couldn’t race her. It’s better to have a backup plan.

Donu & Deca

Donu & Deca are fraternal twins, the youngest of 14 children. Their father was an icosahedron who worked with Gary Gygax and Dave Arneson on the original edition of Dungeons and Dragons, and their mother was a pineapple who mainly stayed home and looked after the children. One of their siblings was a kale who became famous during a recent health food craze. Donu & Deca were sick of living in the shadow of their famous sibling, and moved to the spire to make a name for themselves.

Donu buffs the strength of both shapes while Deca applies two Dazed cards when attacking and can also give block to both shapes. Both shapes start with two stacks of artifact, which can block weak potions among other effects. The attacks are always x2, and there is always exactly one shape attacking on any given turn. Most players prefer to kill Donu first to prevent the strength from getting too high. Once one shape is dead, the other shape sometimes attacks and sometimes uses their ability.

Decks that aren’t aggressive and take a long time to set up have most trouble with this fight, since the constantly increasing strength means it can be over quickly. If you have a Kunai or are in a Barricade-Entrench deck then you can keep ahead of the attacks, but anyone else will just need to race them.

Awakened One

The Awakened One was originally from Australia. She had to evolve the ability to regenerate health and come back from the dead in order to survive among snakes, spiders, crocodiles, sharks, cassowaries, falling cocnuts, razor sharp coral, droughts, flooding rains, and a diet of bread, butter and sprinkles. After surviving being glassed in the belly by a man who’d had one too many Victoria Bitters, she was noticed by some talent scouts and recruited to defend the spire.

She gains 2 strength whenever you play a power, and she has an attack that does x4 damage. This means that each power you play will make you take 8 more damage that turn. The strength gain also persists into the second form. It’s probably not worth it to play defensive powers like Footwork unless you’re playing multiple copies of Dodge and Roll every turn, and it’s almost definitely not worth playing After Image or Metallicize. Have a look at what powers you have, and only play the most essential ones. A single Noxious Fumes will kill her even though she regenerates 10 health per turn, the poison will eventually outgrow the regen. Demon Form and Barricade are also essential powers in their respective decks. Some decks can scale up without using powers, e.g. if your Shiv deck uses J.A.X. to make shivs do more damage, rather than (or as well as) Accuracy.

The downside of this is having to treat powers in your deck like unplayable curses. Once she is in her second form, though, you can play powers without giving her strength. If she dies on your turn, she won’t take any action on her next turn, and then will do the dark echo the turn after. If she dies on her own turn, you will get a turn where she can’t be damaged but you can still play cards. Then on her own turn she’ll come back to life and do the dark echo the turn after.

The second form gives cards that reduce your energy when drawn, and has some strong-ish attacks, but if you survived the first form and didnt give too much strength (and you haven’t been steadily running out of life), you probably shouldn’t have trouble beating the second.

Usually you want to kill the two cultists ASAP, because they are gaining strength, and there’s no point putting incidental damage on the Awakened One that’s just going to get healed. Decks with the Specimen might leave a cultist alive, so that the first form’s poison can be put onto the cultist, and then can be put onto the second form. (The Awakened One loses all debuffs when dying and coming back to life).

Written by Duckie

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