Death Blossom

Death Blossom (also called Aligned ALS Exclusion) is one of the most powerful pattern-based techniques. It features a central "stem" cell connected to multiple "petal" Almost Locked Sets, creating a forcing pattern that guarantees eliminations.

Understanding the Pattern

The Stem

The stem is a single cell with 2-4 candidates. Each candidate connects to a different petal.

The Petals

Each petal is an Almost Locked Set (N cells with N+1 candidates) that:

Contains exactly ONE of the stem's candidates
Shares a common candidate Z with ALL other petals
The common candidate Z is NOT in the stem

The Key Relationship

Number of petals = Number of stem candidates

If the stem has 3 candidates {A, B, C}, there must be exactly 3 petals.

Visual Pattern

                    ┌─────────┐
                    │ Petal 1 │
                    │ {A,Z,...}│
                    └────┬────┘
                         │ sees A
        ┌────────────────┼────────────────┐
        │                │                │
   ┌────┴────┐     ┌─────┴─────┐    ┌────┴────┐
   │ Petal 3 │     │   STEM    │    │ Petal 2 │
   │{C,Z,...}│◄────│  {A,B,C}  │────►│{B,Z,...}│
   └─────────┘     └───────────┘    └─────────┘
    sees C                           sees B

All petals share candidate Z, but the stem does NOT contain Z.

The Forcing Logic

This is why Death Blossom works:

If stem = A: Petal 1 becomes locked → Z is forced somewhere in Petal 1
If stem = B: Petal 2 becomes locked → Z is forced somewhere in Petal 2
If stem = C: Petal 3 becomes locked → Z is forced somewhere in Petal 3

No matter which value the stem takes, Z appears in one of the petals!

Therefore: Any cell that sees ALL Z candidates in ALL petals cannot contain Z.

Example

Stem: R5C5 = {2, 5, 7}

Petal 1: R1C4-R1C5 = {2, 3, 9}     (contains 2 from stem)
Petal 2: R5C1-R6C1 = {5, 3, 8}     (contains 5 from stem)
Petal 3: R8C5-R9C5 = {7, 3, 4}     (contains 7 from stem)

Common candidate Z = 3 (in all petals, not in stem)

Elimination:

Find cells that see ALL instances of 3 in ALL petals
Those cells cannot contain 3

Walkthrough: 2-Petal Death Blossom

This example shows a Death Blossom with 2 petals — the simplest form of the pattern. The stem has 2 candidates, each connecting to a different petal ALS.

puzzle: S9B08372F041Z093N3O3O028J7Z13075ECR5ECQAJ059N024Z4Y036QE2AQ0402081U013M033M3N032R2Q221W7E097E3M082Q09220302013U877P0613BR07BM04BOA69EDQ12024IEA76019V9HDF06BN04DE6C03
mode: guided
technique: DB
initial:
  layers:
    hints: true
steps:
  - text: >
      We're looking for a Death Blossom pattern — a stem cell connected to
      multiple ALS petals that share a common candidate.
    hint: subtle
    technique: DB
    state:
      hint:
        applicationIndex: 13

  - text: >
      **Stem**: R8C4 has candidates {3,5}. This cell will be the centre of our
      Death Blossom. Each candidate connects to a different petal.
    hint: obvious
    technique: DB
    state:
      hint:
        applicationIndex: 13
      selection:
        cells: [R8C4]
      annotations:
        - cells: [R8C4]
          label: "Stem"
          style: pattern

  - text: >
      **Petal A** (digit 3): Cells R1C2, R1C3, R2C2, R2C3, and R3C1 form an ALS
      containing digit 3. This petal connects to the stem via candidate 3.
    hint: obvious
    technique: DB
    state:
      hint:
        applicationIndex: 13
      selection:
        cells: [R1C2, R1C3, R2C2, R2C3, R3C1]
      annotations:
        - cells: [R8C4]
          label: "Stem"
          style: pattern
        - cells: [R1C2, R1C3, R2C2, R2C3, R3C1]
          label: "Petal A"
          style: pattern

  - text: >
      **Petal B** (digit 5): Cells R5C3 and R6C3 form another ALS containing
      digit 5. This petal connects to the stem via candidate 5.
    hint: obvious
    technique: DB
    state:
      hint:
        applicationIndex: 13
      selection:
        cells: [R5C3, R6C3]
      annotations:
        - cells: [R8C4]
          label: "Stem"
          style: pattern
        - cells: [R1C2, R1C3, R2C2, R2C3, R3C1]
          label: "Petal A"
          style: pattern
        - cells: [R5C3, R6C3]
          label: "Petal B"
          style: pattern

  - text: >
      **Common digit Z = 7**: Both petals contain candidate 7, but the stem
      does not. This is the key to Death Blossom — all petals share Z.
    hint: obvious
    technique: DB
    state:
      hint:
        applicationIndex: 13
      selection:
        cells: [R8C4, R1C2, R1C3, R2C2, R2C3, R3C1, R5C3, R6C3]
      focus:
        enabled: true
        digits: [7]
      annotations:
        - cells: [R8C4]
          label: "Stem"
          style: pattern
        - cells: [R1C2, R1C3, R2C2, R2C3, R3C1]
          label: "Petal A"
          style: pattern
        - cells: [R5C3, R6C3]
          label: "Petal B"
          style: pattern

  - text: >
      **Forcing logic**: If stem = 3, Petal A becomes locked → 7 goes in Petal A.
      If stem = 5, Petal B becomes locked → 7 goes in Petal B.
      Either way, 7 must appear in one of the petals!
    hint: obvious
    technique: DB
    state:
      hint:
        applicationIndex: 13
      selection:
        cells: [R8C4, R1C2, R1C3, R2C2, R2C3, R3C1, R5C3, R6C3]
      focus:
        enabled: true
        digits: [3, 5, 7]
      annotations:
        - cells: [R8C4]
          label: "Stem"
          style: pattern
        - cells: [R1C2, R1C3, R2C2, R2C3, R3C1]
          label: "Petal A"
          style: pattern
        - cells: [R5C3, R6C3]
          label: "Petal B"
          style: pattern

  - text: >
      R3C3 sees ALL instances of 7 in both petals. Since 7 must appear in one
      petal, R3C3 cannot contain 7.
      **Eliminate 7 from R3C3.**
    hint: detailed
    technique: DB
    state:
      hint:
        applicationIndex: 13
      selection:
        cells: [R8C4, R1C2, R1C3, R2C2, R2C3, R3C1, R5C3, R6C3, R3C3]
      focus:
        enabled: true
        digits: [7]
settings:
  showCandidates: true
  showControls: true
  showDescription: true
  navigation: numbered

Walkthrough: 3-Petal Death Blossom

This example shows a Death Blossom with 3 petals — demonstrating how the pattern scales. More stem candidates mean more petals, but the logic remains the same.

puzzle: S9B08372F041Z093N3O3O028J7Z13075ECR5ECQAJ059N024Z4Y036QE2AQ0402081U013M033M3N032R2Q221W7E097E3M082Q09220302013U877P0613BR07BM04BOA69EDQ12024IEA76019V9HDF06BN04DE6C03
mode: guided
technique: DB
initial:
  layers:
    hints: true
steps:
  - text: >
      This puzzle contains a 3-petal Death Blossom — a stem with 3 candidates
      connecting to 3 different ALS petals.
    hint: subtle
    technique: DB
    state:
      hint:
        applicationIndex: 2

  - text: >
      **Stem**: R3C8 has candidates {6,7,8}. With 3 candidates, the stem will
      connect to exactly 3 petals.
    hint: obvious
    technique: DB
    state:
      hint:
        applicationIndex: 2
      selection:
        cells: [R3C8]
      annotations:
        - cells: [R3C8]
          label: "Stem"
          style: pattern

  - text: >
      **Petal A** (digit 6): Cells R4C5 and R5C5 form an ALS containing digit 6.
      This petal connects to the stem via candidate 6.
    hint: obvious
    technique: DB
    state:
      hint:
        applicationIndex: 2
      selection:
        cells: [R4C5, R5C5]
      annotations:
        - cells: [R3C8]
          label: "Stem"
          style: pattern
        - cells: [R4C5, R5C5]
          label: "Petal A"
          style: pattern

  - text: >
      **Petal B** (digit 7): Cells R7C2 and R8C2 form an ALS containing digit 7.
      This petal connects to the stem via candidate 7.
    hint: obvious
    technique: DB
    state:
      hint:
        applicationIndex: 2
      selection:
        cells: [R7C2, R8C2]
      annotations:
        - cells: [R3C8]
          label: "Stem"
          style: pattern
        - cells: [R4C5, R5C5]
          label: "Petal A"
          style: pattern
        - cells: [R7C2, R8C2, R9C1, R9C2]
          label: "Petal B"
          style: pattern

  - text: >
      **Petal C** (digit 8): Cells R9C1, R9C2, R8C4, and R8C6 form an ALS
      containing digit 8. This petal connects to the stem via candidate 8.
    hint: obvious
    technique: DB
    state:
      hint:
        applicationIndex: 2
      selection:
        cells: [R9C1, R9C2, R8C4, R8C6]
      annotations:
        - cells: [R3C8]
          label: "Stem"
          style: pattern
        - cells: [R4C5, R5C5]
          label: "Petal A"
          style: pattern
        - cells: [R7C2, R8C2, R9C1, R9C2]
          label: "Petal B"
          style: pattern
        - cells: [R8C4, R8C6]
          label: "Petal C"
          style: pattern

  - text: >
      **Common digit Z = 5**: All three petals contain candidate 5, but the
      stem does not. This is the shared candidate that enables eliminations.
    hint: obvious
    technique: DB
    state:
      hint:
        applicationIndex: 2
      selection:
        cells: [R3C8, R4C5, R5C5, R7C2, R8C2, R9C1, R9C2, R8C4, R8C6]
      focus:
        enabled: true
        digits: [5]
      annotations:
        - cells: [R3C8]
          label: "Stem"
          style: pattern
        - cells: [R4C5, R5C5]
          label: "Petal A"
          style: pattern
        - cells: [R7C2, R8C2, R9C1, R9C2]
          label: "Petal B"
          style: pattern
        - cells: [R8C4, R8C6]
          label: "Petal C"
          style: pattern

  - text: >
      **Forcing logic**: Regardless of which stem candidate is true (6, 7, or 8),
      one petal becomes locked and 5 must appear in that petal. The common
      digit Z=5 is guaranteed to be placed in one of the three petals.
    hint: obvious
    technique: DB
    state:
      hint:
        applicationIndex: 2
      selection:
        cells: [R3C8, R4C5, R5C5, R7C2, R8C2, R9C1, R9C2, R8C4, R8C6]
      focus:
        enabled: true
        digits: [5, 6, 7, 8]
      annotations:
        - cells: [R3C8]
          label: "Stem"
          style: pattern
        - cells: [R4C5, R5C5]
          label: "Petal A"
          style: pattern
        - cells: [R7C2, R8C2, R9C1, R9C2]
          label: "Petal B"
          style: pattern
        - cells: [R8C4, R8C6]
          label: "Petal C"
          style: pattern

  - text: >
      R9C5 sees ALL instances of 5 in all three petals. Since 5 must appear
      in one of the petals, R9C5 cannot contain 5.
      **Eliminate 5 from R9C5.**
    hint: detailed
    technique: DB
    state:
      hint:
        applicationIndex: 2
      selection:
        cells: [R3C8, R4C5, R5C5, R7C2, R8C2, R9C1, R9C2, R8C4, R8C6, R9C5]
      focus:
        enabled: true
        digits: [5]
settings:
  showCandidates: true
  showControls: true
  showDescription: true
  navigation: numbered

Why "Death Blossom"?

The name comes from the visual appearance:

The stem is the centre of the flower
The ALSs spread out like petals
The pattern is deadly to candidates caught in its web

Complexity

Death Blossom is an expert-level technique — arguably the most complex:

Highest difficulty rating (200) of standard techniques
Extremely rare: Appears in less than 0.001% of puzzles
Computationally expensive: Must find and match multiple ALSs
Requires ALS understanding: Built on top of Already Locked Sets

Finding Death Blossoms

Practically, you won't find these manually:

Identify potential stems — Cells with 2-4 candidates
Find ALSs containing stem candidates — Each stem candidate in a different ALS
Check for common Z — All ALSs must share a candidate not in stem
Verify visibility — Stem must see the connecting candidate in each ALS
Find eliminations — Cells seeing all Z instances

This is computationally intensive — let the app find it.

Relationship to Other Techniques

Technique	Pattern
Y-Wing	Pivot + 2 wings (simpler forcing)
Almost Locked Sets	N cells with N+1 candidates
Death Blossom	Stem + multiple ALS petals

Death Blossom is essentially a multi-wing pattern using ALSs instead of single cells.