Slay the Spire Boss Relic Tier List: Best Picks for A20 Runs

This Slay the Spire boss relic tier list ranks all 30 boss relics in the original game for A20 runs. The question is not which relic has the best tooltip. It is which pick gets your current deck through Act 2, the A20 Act 3 boss pair, and the Heart if you are taking the keys.

The tiers are a starting point, not an autopick order. Character, deck, relics, potions, HP, path, and whether the chest is after Act 1 or Act 2 can move any pick. Exact effects are factual; tier placement is editorial judgment.

How this A20 ranking works

• S tier: outstanding in many real runs or powerful enough to reshape a deck.
• A tier: strong picks with a clear condition or manageable cost.
• B tier: good when the deck already supports them.
• C tier: narrow, slow, or expensive in opportunity cost.
• D tier: rarely correct unless the run is already unusually complete.

Three pool rules matter: Ectoplasm is only available from a boss swap or the Act 1 boss chest; character relics only appear for their character; and Black Blood, Ring of the Serpent, Frozen Core, and Holy Water replace their matching starter relics.

Full A20 boss relic tier list

S tier: Coffee Dripper, Cursed Key, Runic Pyramid, Snecko Eye, Pandora's Box, Holy Water, Violet Lotus

A tier: Astrolabe, Fusion Hammer, Slaver's Collar, Empty Cage, Nuclear Battery, Mark of Pain, Hovering Kite

B tier: Calling Bell, Black Star, Philosopher's Stone, Runic Dome, Sacred Bark, Wrist Blade, Inserter, Velvet Choker

C tier: Ectoplasm, Sozu, Frozen Core, Black Blood, Ring of the Serpent, Runic Cube, Tiny House

D tier: Busted Crown

S tier: Run-defining boss relics

Coffee Dripper

Coffee Dripper is premium energy because strong decks already try to spend campfires on upgrades. The extra card you play each turn can prevent more damage than a rest would recover. Sustain from Burning Blood, Reaper, Self Repair, relics, or potions makes the downside easier to cover. Skip it when the deck is already bleeding in ordinary fights; no amount of theoretical value helps if the next bad draw forces a rest you can no longer take.

Cursed Key

Cursed Key gives immediate energy while leaving card rewards, potions, gold, and smithing intact. Its downside is delayed and partly optional: you can skip a chest, remove the curse later, or decide that the relic inside is worth the draw penalty. The danger is opening chests on reflex. One bad curse can do more damage than the chest relic prevents, especially in a small deck or before the Act 4 elites.

Runic Pyramid

Runic Pyramid fixes a central A20 problem: drawing the right card on the wrong turn. It lets Silent hold Piercing Wail or Catalyst, Watcher keep a Wrath exit, and any character save scaling or block for the turn it matters. The cost is hand space. Statuses, curses, expensive cards, and low-impact attacks can clog the ten-card hand limit, so Pyramid wants energy, exhaust, discard, or cheap cards. It does not reduce draw; that was an old effect.

Snecko Eye

Snecko Eye draws two extra cards every turn, while Confused randomizes the cost of cards as they are drawn. That is exceptional with expensive, high-impact cards such as Corruption, Demon Form, Wraith Form, Echo Form, Meteor Strike, Omniscience, or Deva Form. It is much worse when the deck depends on stable zero-cost cards or precise cost-based sequences. Judge the deck you have at the chest; do not take Snecko on the promise that expensive cards will appear later.

Pandora's Box

Pandora's Box removes the weakest part of most decks in one click. More remaining Strikes and Defends means a larger upgrade in average card quality, and Watcher benefits especially because her real card pool outclasses her basics so sharply. The risk is distribution: the transforms can leave you short on block, damage, or reliable first-cycle setup. Check the new deck before choosing an aggressive route, and save potions for the first fights while its shape is still untested.

Holy Water

Holy Water adds two more retained Miracles than Pure Water, giving Watcher three flexible energy for setup, a large Scrawl turn, a safe Wrath exit, or early lethal. That frontload is often worth more than a permanent energy relic during the first decisive turns, and it has no combat penalty. It is not long-fight scaling: once the Miracles are spent, the relic is done. Decks with little draw or nothing valuable to accelerate get less from it.

Violet Lotus

Violet Lotus turns each Calm exit from two energy into three. In a stance-cycling deck, that is recurring energy and sometimes the missing piece of a Rushdown loop. Inner Peace, Fear No Evil, Empty Mind, Tantrum, and other stance tools raise its value quickly. It falls when Calm access is sparse or the deck wins through Divinity, Pressure Points, or straightforward attacks without repeated stance changes.

A tier: Strong picks with clear conditions

Astrolabe

Astrolabe converts three weak cards into three upgraded cards while letting you choose what leaves. It is safer and more controlled than Pandora's Box, especially when only a few starter cards are dragging down the deck. The ceiling is lower because three transforms rarely rebuild an entire run. Take it when card quality and consistency matter more than a fourth energy, but remember that the results are still random.

Fusion Hammer

Fusion Hammer is clean energy when the essential upgrades are already done. It becomes easier to take after Act 2 or with Apotheosis, Armaments, Lesson Learned, upgraded core cards, or non-campfire upgrade events. The relic only disables Smith at rest sites; it does not prevent upgrades from other sources. Pass when cards such as Eruption, Wraith Form, Defragment, Fission, Catalyst, or Limit Break still need their upgrades to carry the deck.

Slaver's Collar

Slaver's Collar supplies energy in the fights most likely to decide an A20 run, including both Act 3 bosses and the Act 4 elite. It has no penalty and gets better when the deck can route through elites. The weakness is the Act 2 hallway pool, where the Collar does nothing. If ordinary fights are already costing large chunks of HP, choose a relic that helps on every floor.

Empty Cage

Empty Cage improves every future draw and can move a compact deck toward a loop. Watcher values removals highly, while any deck with enough power and too many basics appreciates the consistency. The drawback is tempo: two removals do not add energy, damage, block, or a new engine by themselves. Cage is best when the deck already contains its answers and simply needs to draw them more often.

Nuclear Battery

Nuclear Battery provides early energy without a conventional downside. Plasma gives one energy from its passive and two when evoked, so orb cycling can turn it into a controlled burst. It also occupies a slot and gains nothing from Focus, which can delay the Frost or Lightning board a deck wants. Even so, Defect usually has enough orb control to convert the Plasma into a strong setup turn.

Mark of Pain

Mark of Pain is real energy with a first-cycle cost: two Status cards can replace two useful draws before the deck is set up. Ironclad can exhaust the Wounds with Second Wind, Burning Pact, Fiend Fire, or Corruption, and Evolve or Fire Breathing can turn them into value. Without that support, the extra energy may not compensate for missing Shockwave, block, or lethal in a dangerous opening hand.

Hovering Kite

Hovering Kite is close to free energy when Silent already has Acrobatics, Prepared+, Calculated Gamble, Survivor, Dagger Throw, or Tools of the Trade. The first discard each turn triggers it; further discards do not add more energy. Because the energy arrives after the discard, opening sequences can still be awkward. Treat it as A tier with reliable discard access and closer to B or C without it.

B tier: Good when the run supports them

Calling Bell

Calling Bell adds Curse of the Bell, then grants one random Common, one Uncommon, and one Rare relic. The curse cannot be removed, although an unused Omamori charge can prevent it when the Bell is picked up. Three relics are substantial value, but they may not solve the deck's immediate energy, block, or damage problem. It is a solid fallback when the other choices attack a plan that is already working.

Black Star

Black Star is a route commitment, not an immediate power spike. If the deck, HP, and potions can beat elites, the extra relics can snowball the run. If they cannot, Black Star does nothing while Act 2 punishes the missing boss reward. It is strongest after Act 1 with a deck already ahead of the curve. Its bonus does not apply to the Dead Adventurer or Colosseum event fights.

Philosopher's Stone

Philosopher's Stone is reliable energy, but +1 Strength scales with every hit. Byrds, Book of Stabbing, Reptomancer, Awakened One, and the Heart can multiply the downside quickly. Strong Weak, Intangible, Frost, frontloaded damage, or a block engine can absorb it. Avoid the Stone when defense already meets incoming damage by only a point or two; those narrow margins disappear in multi-hit fights.

Runic Dome

Runic Dome is playable when the deck blocks passively, applies long debuffs, or kills before exact intents matter. Knowledge helps with fixed patterns, but it does not remove the downside: many enemy moves are chosen randomly, and Writhing Mass can reroll its intent after taking attack damage. Dome is not merely a memory test. It is hidden information, which makes narrow cards such as Piercing Wail, Dark Shackles, and Spot Weakness harder to time.

Sacred Bark

Sacred Bark can turn saved potions into elite and boss solutions, especially with Alchemize, White Beast Statue, Potion Belt, Toy Ornithopter, or enough gold to shop for refills. Most numeric potion effects double: Ghost in a Jar gives two Intangible, for example. Several utility potions are unchanged, including Ambrosia, Entropic Brew, Gambler's Brew, Smoke Bomb, and Stance Potion. Bark is only as consistent as the potion supply behind it.

Wrist Blade

Wrist Blade adds four damage to each hit of an Attack that costs zero when played. That powers up Shivs, naturally free attacks, and cards reduced to zero by effects such as Setup or Snecko Eye; multi-hit attacks get the bonus on every hit. It is strong when the zero-cost damage shell already exists. Poison or defensive discard decks gain little, so do not take it on the hope of drafting a Shiv deck later.

Inserter

Inserter raises Defect's long-fight ceiling, especially with Focus, Frost, Dark, Plasma, or Consume. The cost is speed. It gives no help on turn one, and extra slots can delay the evocation of an orb the deck needs now. Pick it when early turns are already stable and bosses are the remaining problem. If hallways are killing the deck before its powers come online, Inserter is too slow.

Velvet Choker

Velvet Choker works in decks that play a few expensive, high-impact cards each turn. Its six-card cap is severe for Silent discard or Shiv turns, Watcher stance chains, zero-cost engines, and infinites. Count the cards in your good turns, not just the current average. A deck that plays four cards today may add draw and energy later; Choker can cap the exact growth a boss relic is supposed to enable.

C tier: Narrow, slow, or costly

Ectoplasm

Ectoplasm appears only from a boss swap or after the Act 1 boss, precisely when future gold is most valuable. Losing gold means fewer removals, potions, cards, and shop relics, plus less freedom to route through merchants. Take it when the deck urgently needs energy and has enough current resources to live without later correction. It can win, but it closes more recovery paths than most energy relics.

Sozu

Sozu does not remove potions already held, but it prevents every future potion pickup, including potions from Alchemize and Entropic Brew. That is a major A20 cost: potions cover bad draws, enable elite routes, and solve specific Act 4 turns. Sozu is most defensible with premium potions already saved and a deck that becomes stable on four energy. Even then, every potion used is a resource that can never be replaced.

Frozen Core

Frozen Core trades Cracked Core's starting Lightning for conditional Frost at the end of each turn. Extra orb slots and Focus can turn that into a slow defensive engine, but the relic does nothing when every slot is full and adds no frontload. It fits patient Frost decks that already survive setup. Most Defect decks would rather keep the opening damage and take a boss relic that helps immediately.

Black Blood

Black Blood doubles Burning Blood's post-combat healing from six to 12. That supports aggressive routing and can turn chip damage into a temporary problem, but it adds nothing during combat. If an elite or boss is outscaling the deck, healing after the fight is not an answer. Take it when sustain is the bottleneck and the other choices are actively harmful, not because 12 HP looks large in isolation.

Ring of the Serpent

Ring of the Serpent gives sustained draw but weakens Silent's opening. Ring of the Snake provides two extra cards on turn one; Serpent provides one extra each turn, so total cards drawn only catch up on turn two and pull ahead on turn three. Longer fights benefit, but A20 elites and bosses often punish turn-one setup failures. It is reasonable when energy and defense can exploit the later cards, yet rarely worth a strong boss-relic alternative.

Runic Cube

Runic Cube draws once for each instance of HP loss, including self-damage from Offering, Bloodletting, Hemokinesis, Brutality, or a Pain curse. That can add substantial draw, but it asks the deck to spend health and does nothing when block prevents the loss. Timing also matters: a card drawn from Combust at end of turn is discarded immediately. Cube is useful with deliberate self-damage and sustain, but too conditional for a default boss pick.

Tiny House

Tiny House supplies five small rewards with no direct downside. That makes it a safe exit when the other options would break the deck, and its card reward is a normal three-card choice unless another relic modifies it. The problem is focus: a random upgrade, one potion, 50 gold, five Max HP, and one card rarely solve a specific energy, scaling, or consistency problem. On A20, scattered value is often not enough.

D tier: The default avoid

Busted Crown

Busted Crown cuts a normal three-card reward to one choice. After Act 1, that can erase most of the run's remaining chances to find block, damage, draw, scaling, or a specific boss answer. The energy is real, but the deck-building cost compounds on every combat floor. Take Crown only when the deck is already functionally complete and the remaining plan depends more on playing existing cards than finding new ones. That is rare enough to keep it last.

Quick boss-chest rules for A20

• Need energy now? Start with Coffee Dripper, Cursed Key, Fusion Hammer, Slaver's Collar, and the supported class-energy relics, then price the downside against the next act.
• Too many starter cards? Pandora's Box, Astrolabe, or Empty Cage may improve output more than a fourth energy.
• Holding expensive, high-impact cards? Snecko Eye rises sharply. A deck built around stable zero-cost cards should usually pass.
• Winning through exact sequencing? Runic Pyramid is premium; Velvet Choker and Snecko Eye require more caution.
• Still missing core answers? Be skeptical of Busted Crown, Ectoplasm, and Sozu because they remove ways to repair the deck.
• Considering delayed value? Make sure HP and potions can carry Black Star, Inserter, or Sacred Bark through the next elite first.

The best boss relic is the one that solves the next act without deleting the deck's remaining outs. Start with the tier, then pick for the run in front of you.

Fact-check sources

Effects and availability were checked against the community-run boss relic list, relic pool restrictions, A20 boss rules, and Sacred Bark potion exceptions. Relic icons are Slay the Spire game assets, sourced through the community wiki and a public game-data archive.