The boss checklist that applies to every act
Bosses do not require a different deck from the rest of the run. They reveal the deck job you skipped. Before the final campfire or shop, answer four questions:
- Opening turn: can the deck do enough now, not only after three setup turns?
- Largest intent: can it cover the highest documented attack without drawing perfectly?
- Clock: what ends a long fight—repeatable damage, a scaling engine, or a planned burst?
- Miss: what happens when the answer is not in hand—potion, draw, retain, or acceptable health loss?
The monster database is the fact source for HP, moves, and encounter labels. This page turns that information into a last-minute planning map.
Act 1: Overgrowth and Underdocks
Act 1 rewards cards that work immediately. Take enough front-loaded damage to make the first elite and boss credible, then add block that does not cost the whole turn. A slow payoff is fine only after the deck can survive the floor where it was offered.
| Boss | Area | What to prepare | Move data |
|---|---|---|---|
| Ceremonial Beast | Overgrowth | A clean answer to repeating pressure; do not enter with only greedy setup | Open entry |
| Kin Follower | Overgrowth | Damage and a stable defensive hand | Open entry |
| Kin Priest | Overgrowth | A plan for debuffs and the long turn after them | Open entry |
| Vantom | Overgrowth | Enough immediate damage to avoid falling behind | Open entry |
| Lagavulin Matriarch | Underdocks | Use the opening space to set up only if the next turn remains safe | Open entry |
| Soul Fysh | Underdocks | Flexible defense and a damage clock through the sequence | Open entry |
| Waterfall Giant | Underdocks | Preserve a response for the heavier physical turns | Open entry |
For route-level decisions, use the Act 1 boss preparation guide and Act 1 pathing checklist. The right upgrade is often the one that makes the next tough turn less awkward, not the one that looks strongest in a vacuum.
Act 2: Hive
By Act 2, “I have damage” is not a complete plan. The deck needs draw quality, scaling, or enough block repetition that a bad shuffle does not turn into a potion emergency.
| Boss | What it exposes | Move data |
|---|---|---|
| Crusher | Decks that cannot cover repeated pressure while advancing a win condition | Open entry |
| Knowledge Demon | Poor curse handling and hands that lose function under disruption | Open entry |
| Rocket | A missing answer to telegraphed burst turns | Open entry |
| The Insatiable | Weak sustain, slow damage, or no plan for its repeating sequence | Open entry |
Do not respond by drafting every defensive card. Improve the card that makes the existing engine happen on time: draw finds the answer, Energy plays it, and removal increases the chance it matters. The Act 2 boss guide has a focused mid-run checklist.
Act 3: Glory
Act 3 bosses ask whether the run has become coherent. You need a damage clock and a defensive loop that can survive while that clock works. One enormous turn is useful; a deck that cannot recover after it is not finished.
| Boss | What to respect | Move data |
|---|---|---|
| Aeonglass | Repeating Ebb, Eye Lasers, and Increasing Intensity pressure; bring defense plus a real clock | Open entry |
| Queen | The fight changes around the Amalgam state; check the current entry before building a fixed script | Open entry |
| Test Subject #C14 | A plan that survives its later conditional attacks, not just the opening | Open entry |
| Torch Head Amalgam | Enough repeatable defense to remain functional through its sequence | Open entry |
Aeonglass deserves extra attention because a deck can look powerful and still lose if it needs too many uninterrupted setup turns. Read the current Aeonglass guide alongside its database entry before choosing your final shop purchase.
Potion and campfire decisions
Give each potion a job. “Save it for the boss” is not a job; “cover the biggest documented hit,” “buy one setup turn,” or “finish the boss before the pattern repeats” is.
At the final campfire, upgrade when it changes one of the four checklist answers. Rest when a normal bad draw is lethal. Remove when the deck has the answers but cannot find them. The potion guide and boss preparation checklist make those choices more concrete.
Keep this page current
Slay the Spire 2 is in Early Access, and boss values or patterns can move. This page deliberately links to the database instead of freezing every number into prose. Check the individual monster entry before a serious run, and use the patch notes hub when main-branch and beta guidance disagree.
