Multi-Phase Boss Framework

A modular multiphase boss design tool built on the 09 series' role contracts and Key system. Not a rulebook — a toolbox: for each boss, the trigger, HP structure, change axis, and action economy are each chosen separately.

Contents

1. Core Contract
2. Module 1 — Phase Triggers
3. Module 2 — HP Structures
4. Module 3 — Inter-Phase Change Axes
5. Module 4 — Action Economy
6. Transition Moment Rule
7. CR Calibration — Three Methods Compared
8. Example 1 — Bone Puppeteer (T2, two-phase, new)
9. Example 2 — Peak Tyrant Transformation (T4, three-phase, old↔new)
10. Quick Design Checklist

Core Contract

Every monster in the 09 series had a single Key: the party's path to victory. The multiphase boss expands this as follows:

Every phase has its own Key. A phase is a monster.

This produces three consequences:

1. Number of phases = number of keys. A two-phase boss asks the party two puzzles; a three-phase boss asks three. A boss fight is not an HP bar — it is a sequence of consecutive puzzles.
2. The role contract applies within a phase. A boss that is a Lurker in Phase 1 acts like a Lurker and carries the Lurker brake (Ambush Predator tied to stealth). If it becomes a Brute in Phase 2, it is now under the Brute contract.
3. Tier determines the number of phases:

Key telegraph rule (3 clues)

A key does not exist if the party cannot find it. Each phase's key must be readable through at least three channels, either before the fight begins or during the phase:

1. Visual — a physical marker present in the arena (cracks in ice armor, trembling of bone pillars)
2. Behavioral — the boss avoiding the key (never leaving the fog, flinching from fire)
3. Knowledge — lore, an NPC, a previous encounter, or a successful Arcana/Nature check

If the party fails to find the key despite the three clues, the fight must still be winnable — it just becomes longer and more costly. The key is not a door, it is a shortcut.

Module 1 — Phase Triggers

Four models. For each boss, choose one per phase; the same boss can use a different trigger for different phases.

1A — HP Threshold

When the boss's HP drops below a certain threshold (usually 50% or 40%), the phase changes.

• Strength: Predictable, easy to calculate, works with any party composition.
• Weakness: Asks the party no decisions at all — it only says "deal damage." Nova parties pierce the threshold in a single turn, seeing two phases in the same round.
• Nova insurance: Add the line "the boss cannot skip more than one phase in a turn; excess damage is lost when the threshold is exceeded."
• When to use: When the phase transition must be guaranteed (the finale's 3rd phase must never be skipped).

1B — Key Break

The phase changes when the party solves that phase's key. HP is secondary.

• Strength: The most natural match with the Key system: solving the puzzle = closing the curtain. The party feels clever.
• Weakness: If the key can't be found, the fight locks up. Always set a backup threshold: "Even if the key isn't solved, the phase changes when HP drops to 25%" — but on this path the transition costs the party dearly (the boss enters empowered; see Module 3 below).
• When to use: When the key itself carries staging value (the fog dispersing, the armor melting is a visual moment).

1C — Arena / Target-Based

The phase changes when an object in the arena (pillar, altar, crystal, rope) is destroyed or a target is completed.

• Strength: Adds a second front to the fight: who's hitting the boss, who's hitting the pillars? It asks a question of positioning and division of labor. The boss may even be untouchable (a boss that can't be hit in Phase 1 comes down once the pillars break).
• Weakness: Requires prep — a map of the arena, AC/HP of the objects. If the objects are ignored the fight stalls (the boss must actively use the objects: drawing power from the pillars, healing from the altar).
• Object calibration: Object AC = party level + 8; Object HP ≈ level × 4; the target should take "1.5 turns of one character."
• When to use: When the arena will be the fight's defining character. Use this if you want them to remember the scene, not the boss.

1D — Mixed

Multiple triggers for the same transition: "50% HP or key break — whichever comes first."

• Strength: A two-door room: the clever party enters through the key (fast, cheap), the brute-force party enters through HP (slow, costly). Both playstyles work.
• Design rule: The two doors must not be equal. The key door should always be cheaper — otherwise no one bothers solving the puzzle. Make it concrete: "Entering via the key means the boss enters Phase 2 wounded (−30 HP) / entering via HP means it enters at full strength."
• When to use: As the default choice. This framework's standard is 1D; 1A–1C are for special cases.

Module 2 — HP Structures

Three models. The choice depends on Module 1's trigger — the matching table is below.

2A — Single Pool, Thresholded

The boss has a single HP pool; phases are separated by thresholds (232 HP → Phase 2 at 60%, Phase 3 at 25%).

• The easiest model to track. Pairs naturally with the HP Threshold (1A) and Mixed (1D) triggers.
• Total HP should be 100–115% of the nominal CR's SRD average — the phases already lengthen the fight, don't inflate HP.

2B — Separate Pool Per Phase

Each phase has its own HP; the previous phase's leftover doesn't carry over.

• Pairs naturally with the Arena trigger (1C): the Phase 1 body is a fragile 60-HP thing that can't be hit; the Phase 2 body is a new 110-HP form.
• Nova-friendly: no matter how fast the party clears Phase 1, Phase 2 starts at full. This gives confidence in finales, but doesn't reward the party's "early damage" — choose this knowingly.
• The sum of the pools can be 110–130% of the nominal CR average (the transition break between them gives the party breathing room).

2C — Mythic Renewal

The boss "dies," then rises again with a small pool (30–40% of nominal).

• The most dramatic model — and the riskiest: the party experiences the joy of "we won" and then has it taken back. Use it at most once or twice in a campaign, or they'll stop believing in any death.
• Telegraphing is mandatory: give the sign before the rise (light leaking from the disintegrating body, an unfinished ritual).
• Use only for the final phase. Mythic in a middle phase blurs the structure.

Matching table

Module 3 — Inter-Phase Change Axes

What changes at the phase transition? Three axes; choose one or two per boss. Don't change all three — if the party loses everything it learned, the transition feels like a punishment.

3A — Role Shift (the strongest axis)

The boss changes its role contract: Lurker → Brute, Controller → Skirmisher.

• Deliberately invalidates the party's Phase 1 plan: the wizard who dispersed the fog faces a completely different problem in Phase 2.
• Rule: The new role must also have its own brake. As a Lurker it was tied to stealth; as a Brute it must also carry a new key (an elemental weakness, range, speed).
• Ideal transitions are built on contrasts: hidden → visible, fast → slow-heavy, distant → close.

3B — Empowerment (role fixed)

The role stays the same; the numbers and abilities grow (a new attack, Recharge improves, extra movement).

• The safest axis: the party keeps using what it learned, it just gets harder.
• Used alone, the phase transition can feel like "more of the same fight" — support it with a visual change (armor cracks, flames grow).

3C — Arena Shift (the monster is fixed)

The boss stays the same; the scene changes: the floor collapses, water rises, the room narrows, the light goes out.

• Very strong with bosses that play a positioning game (Skirmisher, Artillery).
• The key can be tied to the arena: Phase 2's key is a new feature of the arena ("the stone platform in the middle of the rising lava is the only safe firing point").

Mixed usage: In a T4 three-phase boss, a typical sequence is: Phase 1→2 role shift (3A), Phase 2→3 arena shift + empowerment (3B+3C).

Module 4 — Action Economy

The real math of boss fights isn't HP, it's turn count: a 4–5-person party gets 4–5 turns per round; a single boss gets 1. If this gap isn't closed, the boss gets crushed no matter its CR. Three models:

4A — Legendary Actions (classic)

3 Legendary Actions per round; the boss acts at the end of others' turns.

• Tried and true, everyone knows the system. Cost table: weak action 1, medium 2, strong 3.
• Phase integration: The Legendary list should change along with the phase. Phase 1 Lurker's legendary is "Hide + move"; Phase 2 Brute's is "extra attack."

4B — Phase-Based Reaction Set

Instead of Legendary, the boss carries 2–3 special Reactions per phase and can use more than one Reaction per round (once per trigger).

• Makes the boss reactive: the boss responds as the party does things. "When a spell is cast," "when someone approaches," "when it takes damage."
• Less of a "boss is everywhere" feel, more of a "we're stripping the boss's shields" feel. Works well with Controllers and Lurkers.

4C — Lair + Legendary Together

At Initiative 20, Lair Action (arena attacks) + 3 Legendary (boss attacks).

• The highest pressure — use only in T3–T4 finales. In T2 the party's resources can't handle it.
• Lair Actions should be the arena-changing kind (combines with Module 3C): a collapsing floor is both damage and a new scene.

Selection guide: T2 → 4A or 4B (alone). T3 → 4A + weak lair. T4 → 4C. If the boss has minions, drop one tier — minions already close the turn gap.

Transition Moment Rule

A phase transition is not a mechanical line, it's a scene. The following package applies at every transition:

1. Cleanup: All conditions on the boss (Grappled, Restrained, Prone, spell effects) end. Concentration spells aren't broken, but they no longer affect the boss. (Rationale: don't let the boss spend Phase 2's first turn still in Phase 1's chains — the new act starts clean.)
2. Repositioning: The boss moves up to 60 feet for free, or teleports to its dramatic point in the arena. No Opportunity Attack is triggered.
3. Recharge: All Recharge abilities refill.
4. Telegraph turn (MANDATORY). The boss's first turn after the transition is a showcase turn — it uses the new phase's most visual ability but stays under the full damage band (rough rule: halve that turn's damage output, or delay the strongest attack to the next turn). The party learns the new rules without dying. (A 72,000-fight A/B test showed this raised win rate by ~+26 points for parties in the critical band, while breaking nothing at either extreme — see 17b_Boss_Telegraf_AB_Testi. This is why it's mandatory, not optional.)
5. Key clue: The transition scene must include the first clue to the new phase's key (the 3-clue rule begins here).

CR Calibration — Three Methods

A multiphase boss's CR doesn't fit a single number; there are three calculation methods. Each is covered first, then a comparison.

Method A — CR Per Phase ("phases are separate monsters")

Calibrate each phase like an independent monster: AC/HP/damage band sits at that phase's own CR's SRD average. The total encounter is budgeted as "back-to-back short encounters."

• Calculation: The phases' total XP ≈ 1.3–1.5 times a single Deadly encounter (no rest in between, but Transition Moment cleanup gives a breather).
• Example (T2, level 7, 4 people): Deadly ≈ 6,800 XP → target total ≈ 9,000–10,000 XP → Phase 1 CR 4 (1,100) isn't enough; in practice Phase 1 CR 6 (2,300) + Phase 2 CR 8 (3,900) ≈ 6,200 XP, filled out to 9,000 with minions and arena hazards.
• Strength: The most accurate result — each phase sits directly on the 09 series' calibration tables, fully compatible with the existing system.
• Weakness: The most calculation-heavy method.

Method B — Total Budget ("nominal CR" shortcut)

A single formula: Boss nominal CR ≈ party level + number of phases. Then split across phases: the final phase sits at nominal CR, each previous phase is 1–2 CR lower than the one after it.

• Example (T4, level 18, 3 phases): Nominal CR ≈ 21 → phases CR 17 → 19 → 21 or flat 18/18/18.
• Example (T2, level 7, 2 phases): Nominal CR ≈ 9 → phases CR 7 → 9.
• Strength: Calculated at the table in 10 seconds. Use this when you need an improvised boss mid-session.
• Weakness: Crude. Doesn't see party composition, minions, or the arena. Always test the result against Method C's numbers.

Method C — Splitting SRD Calibration Across Phases (number distribution)

Take the nominal CR's SRD average values and distribute them proportionally across phases:

• Example (nominal CR 16, three phases): SRD: AC 19 / HP 232 / band ~90. → Total HP 232 × 1.2 ≈ 280 → phases 112 / 98 / 70. Damage band 72 → 85 → 95.
• Strength: Directly produces the numbers; a natural extension of the existing calibration tables.
• Weakness: Doesn't state the phases' CR "identity" — it doesn't answer "what CR monster is Phase 1?", it just distributes numbers.

Comparison and recommendation

This framework's standard: Build the skeleton with B (nominal CR and phase CRs), fill in the numbers with C (HP/AC/band distribution), verify with A before publishing (does each phase sit on its own CR average?). The two examples below are calculated with this three-step flow, with every step shown.

Example 1 — Bone Puppeteer

(T2 · two-phase · new design · Dungeon/Structure)

Design decisions (module choices)

CR calculation (B → C → A flow)

• B: Level 7 party, 2 phases → nominal CR ≈ 9 → phases CR 5 → CR 8 (Phase 1's boss is kept one tier lower since it can't be hit; the puppets supply the pressure).
• C: Total HP target: CR 9 average 162 × 1.15 ≈ 186 → Phase 1: 68 (pillars separate) + Phase 2: 118. Damage band: Phase 1 ~80% (including puppet attacks), Phase 2 ~105%.
• A verification: The Phase 1 profile sits on the CR 5 average (AC 15 / HP ~97 — here 68, because it's already hard to hit), the Phase 2 profile sits on the CR 8 average (AC 16-17 / HP ~150 — here 118 + Phase 1 attrition). Total XP ≈ 1,800 + 3,900 = 5,700; effectively ~8,500 with pillars and puppets — level 7 Deadly ×1.3. ✅

Bone Puppeteer — PHASE 1: "Choir Conductor"

Medium Undead, Neutral Evil · Role: Controller · Phase CR 5 (PB +3)

AC 15 · Initiative +5 (15) HP 68 (behind the bone cage; see below) Speed 30 ft.

Skills Arcana +6, Perception +5 Immunities Poison; Charmed, Exhaustion, Frightened, Poisoned Senses Darkvision 120 ft.; Passive Perception 15 Languages Common, Necril Phase CR 5

Arena — Three Bone Pillars

Three pillars stand across the room (AC 15, HP 30, immune to Poison/Psychic). As long as the pillars stand, the Puppeteer is inside a bone cage: it cannot be targeted and is unaffected by area damage.

• Whenever a pillar falls: the Puppeteer loses one Bone Puppet it's currently operating (3 → 2 → 1), and the cage visibly cracks. (Telegraph: the party sees its progress.)
• When the third pillar falls → Phase 2 triggers.

Traits

Bone Choir. The Puppeteer operates 3 Bone Puppets (below) in the arena. The puppets act on the Puppeteer's initiative. A destroyed puppet is reborn from a standing pillar on the Puppeteer's next turn (one per pillar per round).

Puppet Strings. Puppets must stay within 60 feet of the Puppeteer; a puppet that leaves this range collapses.

Bone Puppet (minion)

Medium Undead · AC 13 · HP 22 · Speed 30 ft. · Saves +0 Claw. Melee: +5, 5 ft. Hit: 8 (1d10 + 3) Slashing. If two puppets are adjacent to the same target, their attacks are rolled with Advantage.

Actions (Puppeteer)

Bone Throw. Ranged Attack Roll: +6, range 60 ft. Hit: 13 (3d6 + 3) Piercing damage.

Grave Command (Recharge 5–6). An enemy within 60 feet makes a DC 14 Wisdom save. Failure: On its next turn it cannot move and uses its action to make a single weapon attack against its nearest ally (the strings tangle it too). Success: No effect.

Reactions (Phase-Based Set — each usable once per round)

String Yank. When an enemy attacks a pillar: one Bone Puppet may move up to 15 feet toward that enemy and make one Claw attack.

Bone Curtain. When an attack hits the Puppeteer (through the cage's cracks): it transfers the damage to a puppet (the puppet takes the damage).

Bone Puppeteer — PHASE 2: "Choir Body"

Transition Moment: The third pillar topples. Every bone in the room — pillar wreckage, destroyed puppets, the floor tiles — merges around the Puppeteer into a Large giant's body. Conditions are cleared; the giant steps into the middle of the room. Telegraph turn: on its first turn it only uses Bone Wave, opening three cracks in the floor — spinal joints show through the cracks. (Key clue 1.)

Large Undead, Neutral Evil · Role: Brute · Phase CR 8 (PB +3)

AC 16 · Initiative +3 (13) HP 118 Speed 30 ft.

Resistances Piercing, Slashing (nonmagical) Vulnerabilities Bludgeoning Immunities Poison; Charmed, Exhaustion, Frightened, Poisoned Senses Darkvision 120 ft.; Passive Perception 15 Phase CR 8

Traits

Loose Joints. The Choir Body is Vulnerable to Bludgeoning damage (its joints scatter). Also, if it takes 25+ Bludgeoning damage in a turn, it cannot Multiattack on its next turn (it reassembles itself).

Actions

Multiattack. Two Crushing Fists.

Crushing Fist. Melee Attack Roll: +8, reach 10 ft. Hit: 18 (3d8 + 5) Bludgeoning damage; the target makes a DC 16 Strength save, Failure: Prone.

Bone Wave (Recharge 5–6). 15-foot Cone; DC 15 Dexterity save. Failure: 22 (5d8) Piercing damage and pushed back 10 feet. Success: Half damage.

Legendary-lite (2 per round)

Step. Moves 15 feet. Fist (2 actions). One Crushing Fist attack.

How to use & keys

Phase 1 key: "Break the pillars" — the key is the trigger itself (the nature of Model 1C). If the party tries to hit the Puppeteer they hit a wall; the fight is a problem of getting damage to the pillars while the puppets apply pressure. The String Yank reaction punishes whoever breaks a pillar — the tank takes the pillar, the others take the puppets.

Phase 2 key: "Bludgeoning" — the SRD skeleton classic at boss scale. The Cleric with a warhammer is this phase's star; their damage doubles and the 25+ threshold strips the boss's Multiattack. A party without Bludgeoning still wins — it just pays the full price for 118 HP.

Telegraph chain: (1) the spinal joints visible at the opening of Phase 2, (2) the giant's visible shudder on the first Bludgeoning hit ("bones rattling apart"), (3) Arcana/Religion DC 13: "bone structures are ill-suited to crushing blows."

Example 2 — Peak Tyrant Transformation

(T4 · three-phase · transformation of an existing boss · Mountains/Hills)

Before: the single-phase original (summary)

Its form from 09g Section C: CR 16, Lurker, AC 19 / HP 232. Its loop: Cloud Veil → Vanish → Ambush Predator (+33) → Stoop (grab-carry-drop). Single key: take the fog (Gust of Wind etc.), break its wing (Earthbind etc.).

The limit of the single-phase form: If the party solves the key early (round 1's Gust of Wind + Earthbind), the CR 16 boss turns into an ordinary dragon, and the remaining 200+ HP is replaying an already-solved puzzle. Multiphase solves exactly this problem: solving the key doesn't end the fight, it closes the curtain.

Design decisions

CR calculation (B → C → A flow)

• B: Level 18 party, 3 phases → nominal CR ≈ 21 → phases CR 16 → 18 → 15 (the final phase is the mythic death-throes; the peak is Phase 2 — "a wounded dragon is the most dangerous").
• C: Nominal CR 21 SRD average ≈ AC 21 / HP 336. Total HP: 336 × 1.1 ≈ 370 → Phase 1: 150 / Phase 2: 130 / Phase 3: 90 (mythic). AC shifts a lot: 19 → 17 (armor cracks) → 15 (form disperses). Damage band: 90 → 105 → 80 + arena.
• A verification: Phase 1 = CR 16 Lurker profile (the original itself, with a shortened pool). Phase 2 = CR 18 Brute band (~105/turn ✅). Phase 3 = CR 15 Controller + lair pressure. XP ≈ 15,000 + 20,000 + 13,000 = 48,000 ≈ level 18, 4 people, Deadly ×1.5. ✅

PHASE 1 — "Fog King" (Lurker · CR 16 · HP slice 150)

The original stat block is played as-is (AC 19, attacks, Mountain Shadow, Ambush Predator, Stoop, Cloud Veil) — the only difference is the HP slice.

Lair Action (Initiative 20, optional): Fog wall (a 60 ft radius Heavily Obscured area shifts) or Rockfall (20 ft square, DC 20 Dex, 22 Bludgeoning).

Phase 1 key (original): Take the fog, break the wing.

Transition (Mixed, two doors):

• Key door: If, in the same round, the party (a) disperses the fog/cover and (b) grounds the Peak Tyrant → Phase 2 starts at −30 HP (fall damage; scene: the dragon slams onto its back).
• HP door: If the Phase 1 slice (150) runs out → Phase 2 starts at full strength.

PHASE 2 — "Broken Wing" (Brute · CR 18 · HP slice 130)

Transition Moment: The Peak Tyrant slams onto its back; one of its wings is bent at an unnatural angle. Conditions are cleared; a body of ice covers its form. Telegraph turn: on its first turn it doesn't attack — it roars, and the Thin Air area turns into a visible ring of pressure; melted droplets glisten on the ice armor. (Key clue 1: temperature.)

Changed values: AC 17 (armor is rough but cracked) · No Fly, Speed 50 ft. · Damage band ~105.

New/changed abilities

Ice Armor. During Phase 2, the Peak Tyrant loses HP equal to double the Fire damage it takes (an effective Vulnerability); also, if it takes 30+ Fire damage in a turn, its AC permanently drops to 15. (Phase 2 key.)

Multiattack. One Bite + two Talons + a Tail (new: +12, reach 20 ft., 20 (3d10+5) Bludgeoning, DC 20 Str save or Prone).

Avalanche Charge (replaces Stoop). Runs up to 40 feet in a straight line; everyone in the line makes a DC 20 Str save — Failure: 33 (6d10) Bludgeoning + Prone; if near the edge, they're swept off it.

Killing Wind stays the same (Thin Air's Disadvantage is still active) — but now comes from a body that cannot flee.

Legendary (3/round): Tail (1) · move 20 ft (1) · Killing Wind re-roll (2, once per round).

Phase 2 key: Fire. Melt the ice armor — this both doubles the damage and cracks the AC. A boss that had Cold resistance in Phase 1 opening up to fire in Phase 2 is the 3A contrast principle: the party is forced to rethink its toolbox.

Transition: When the Phase 2 slice (130) runs out → Phase 3.

PHASE 3 — "The Peak's Last Breath" (Controller · CR 15 · Mythic 90 HP)

Transition Moment (Mythic): The Peak Tyrant's body disperses — the party briefly thinks it has won. Then snow, ash, and freezing wind gather into the dragon's silhouette, rewoven from the storm. (The mythic telegraph was given throughout Phase 2: snow scatters from its body on every hit taken, "as if there's a storm beneath the flesh".) The arena changes: the peak itself is caught in a storm — vision drops to 30 feet, the outer 15 feet of the ridge ices over every round (Difficult Terrain, DC 15 Dex or Prone).

Values: AC 15 · HP 90 · Fly 60 ft. (hover, storm form) · Resistance to nonmagical B/P/S damage.

Eye of the Storm. The area within 15 feet of the Peak Tyrant is calm: vision is normal, there's no icing, and Thin Air does not function there. An enemy standing outside the eye has Disadvantage on attack rolls against the Peak Tyrant (the storm's veil obscures vision). (Note: this only affects attack rolls; it has no bearing on saving throws.)

Actions: Freezing Claw (+10, reach 10 ft., 26 (4d10+4) Cold) ×2 · White Death (Recharge 5–6): every creature within the storm area (i.e. outside the eye) makes a DC 18 Con save. (Phase 2's Thin Air is gone now; this save is rolled straight — Eye of the Storm's Disadvantage only applies to attack rolls, so it isn't relevant here.) Failure: 45 (10d8) Cold + Speed halved. Creatures inside the eye are unaffected.

Lair (Initiative 20): The storm shrinks by 10 feet (the outer ring grows) — the arena shrinks every round.

Phase 3 key: "Enter the eye." The only safe place is right at the dragon's base — the inverse of the "keep your distance" key: a party fighting from range drowns in the storm; a party that closes to melee sees normally, hits normally, and is unaffected by White Death. The finale ends with everyone chest to chest, in the dragon's shadow. (Telegraph: the calm inside the eye is described during the transition scene; Nature DC 15: "the eye of a storm is always still.")

Old ↔ New comparison

The essence of the transformation: The original key wasn't erased — it became Phase 1's key. The multiphase structure is built on top of a well-designed single-phase boss; it doesn't replace it, it writes its sequel.

Quick Design Checklist

When building a new multiphase boss, in order:

1. Tier → number of phases (T2: 2, T4: 3)
2. Write a role + key for each phase (phase = monster; choose from the key table's families: Fire, Cold, Bright Light, Bludgeoning, "approach," "stop," "get out of the water"…)
3. Build contrast between phases (1–2 axes from 3A/3B/3C; never all three)
4. Choose the triggers (default: 1D Mixed; the key door is always cheaper)
5. Match the HP structure (Module 2 table)
6. CR: build with B → fill with C → verify with A
7. Action economy (T2: 4A/4B · T4: 4C; drop one tier if there are minions)
8. Write Transition Moments as scenes (cleanup + repositioning + recharge + mandatory telegraph turn + first clue)
9. Place 3 clues for each key (visual / behavioral / knowledge)
10. Nova test: what happens if the party does everything in round 1? If the answer is "the fight collapses," go back to step 4.

Calibration: All AC/HP values and damage bands are based on per-CR averages calculated from SRD 5.2's 318 monsters (CR 5 → AC 15 / HP 97 · CR 8 → AC 16 / HP 152 · CR 15 → AC 18 / HP 213 · CR 16 → AC 19 / HP 232 · CR 18 → AC 19 / HP 279 · CR 21 → AC 21 / HP 336).

License: This framework and stat blocks are original works. Rule terms and mechanics are based on SRD 5.2 (Wizards of the Coast LLC, CC-BY-4.0). This work includes material from the System Reference Document 5.2 ("SRD 5.2") by Wizards of the Coast LLC, available at https://www.dndbeyond.com/srd. The SRD 5.2 is licensed under the Creative Commons Attribution 4.0 International License, available at https://creativecommons.org/licenses/by/4.0/legalcode.