Npc

creatures/**/<id>.srd.ron — one per file; stem == id. PRIMITIVES ONLY; composites derive (README "Derivations").

Field	Type	Required	Description
abilities	any[][]	required	Base ability scores, BEFORE racial adjustments.
alignment	AlignmentConstraint	required	The block's alignment line as a generation constraint, not a value.
armor	string[]	required	Armor ids, boot-resolved; empty = unarmored.
attacks	NaturalAttack[]	optional	The monster's natural attacks — read at combatant assemble so it strikes with its own bite/claw/slam, not a borrowed weapon. Empty on the humanoid blocks (they fight with `weapons`).
blindsight	integer	optional	Blindsight radius in feet; absent = none.
breath	MonsterBreath	optional	The monster's Breath Weapon — a recharge area-save action (the black dragon wyrmling's Acid Breath, the magma mephit's Fire Breath). ABSENT = none (every humanoid block and most monsters). Assembled into a charged `BreathReady` at bubble open and loosed by the AI like the dragonborn's, but it returns MID-FIGHT on the Recharge roll, not a rest.
condition_immunities	string[]	default []	Conditions this creature can never suffer — `conditions/` ids, checked at the `Afflict` inflict point so an undead is never poisoned and a construct never frightened. Ids resolve against the shipped catalog; SRD immunities to LEDGERED conditions (exhaustion, charmed, deafened) are noted in the file, not listed here.
cr	string	required	The cr_xp key, boot-resolved — the stored primitive that feeds xp(cr).
creature_type	string	required	A `tables/creature_types.srd.ron` id, boot-resolved — the stat block's "Type" line. The seeded blocks are all `"humanoid"`; the bestiary's typed monsters declare their own.
darkvision	boolean	default false	SRD senses off the stat block's "Senses" line — darkvision (a bool presence flag; monsters are raceless so it rides the block, not a composed race) and the special senses in FEET of radius. Stamped at `instantiate_creature`, read by `soul::senses_of` and `light::seen`. ABSENT = none. The bestiary prints these where the SRD does; no HUMANOID block carries a special sense (sim-neutral).
id	string	required
immunities	string[]	default []	SRD damage immunities / vulnerabilities on the creature stat block — damage-kind ids, read at bubble assemble like the kit (`damage_mods_at`): immunity zeroes the kind, vulnerability doubles it. The typed monsters carry them (a skeleton's poison, a mephit's fire); no HUMANOID block does (sim-neutral). Absent = none.
languages	string[]	default []	SRD known languages off the stat block — `languages.srd.ron` ids, stamped at `instantiate_creature` (`LANGUAGES`). ABSENT MEANS COMMON (the absent-default). The seeded HUMANOID blocks declare none (Common by construction); a typed monster may name its own tongues.
level	uint32	required	Level == hit-dice count.
multiattack	integer	optional	Attacks one Attack action makes — the printed Multiattack count, wired into the NPC turn like Extra Attack. ABSENT = one. A conditional/compound multiattack (grick's beak-on-hit, a dragon's distinct bite+claws) is LEDGERED — this is the simple count.
natural_armor	integer	optional	SRD natural armor: the AC base a monster's hide/scales/plating gives, to which its Dex mod adds (`na + dex_mod`) — the README's named "stored exception" to the derivation. ABSENT = unarmored (`10 + dex_mod`), the zombie/ooze case.
proficiencies	Skill[]	required	The skill-proficiency SET; bonuses derive.
resistances	string[]	default []	SRD damage resistances on the creature stat block — damage-kind ids taken at HALF, read at bubble assemble beside the composed race/class resistances (a dretch halves fire, a gray ooze halves acid/cold/fire). Absent = none. The "from nonmagical attacks" qualifier a few blocks carry is LEDGERED (no magical-weapon distinction yet) — such a resistance is listed plainly or noted in the file.
size	Size	optional	A monster's OWN size — monsters are raceless, so there is no composed race to derive it from; the hit die swings by it. ABSENT means the humanoid "(any race)" assumption (size comes from the composed race, Medium in the printed corpus) — no humanoid block carries it.
source	Source	required
speed	integer	optional	A monster's OWN speed in feet — raceless, so stamped from the block. ABSENT = the composed race's speed (the humanoid blocks).
tremorsense	integer	optional	Tremorsense radius in feet; absent = none.
truesight	integer	optional	Truesight radius in feet; absent = none.
vulnerabilities	string[]	default []	Damage-kind ids taken at DOUBLE; absent = none.
weapons	string[]	required	Weapon ids, boot-resolved.

Nested shapes

Every shape Npc closes over, so this page stands alone.

Ability

The six ability scores (SRD 5.1). The engine's own stats::Ability is the runtime type; this is the data-layer mirror, bridged by [Ability::engine].

StrDexConIntWisCha

AlignmentConstraint

The blocks' printed alignment lines as generation constraints (README).

AnyNonLawfulNonGoodChaotic

Damage

Field	Type	Required	Description
dice	string	required	The damage dice, an `NdM` string (e.g. "1d8").
kind	string	required	A `tables/damage_kinds.srd.ron` id, boot-resolved.

MonsterBreath

A MONSTER's Breath Weapon DATA — the recharge area-save action the bestiary blocks ledgered. Unlike the racial breath (dice by level, DC by Con), a monster's stat block PRINTS its damage dice; the SAVE ability is data too, and the DC DERIVES at assemble (8 + pb_for_cr(cr) + Con mod — the CR proficiency, which reproduces the printed value). The area is the archetypal 15-ft cone (the SRD per-monster line/cone split stays LEDGERED).

Field	Type	Required	Description
damage	Damage	required	The printed damage — dice + a `tables/damage_kinds.srd.ron` kind (validator-checked); a failed save takes it whole, a success half.
recharge	uint32	required	The LOW bound of the SRD recharge range (5 = "Recharge 5-6", 6 = "Recharge 6") — the breath returns on a d6 ≥ this at the breather's turn start. In 1..=6 (validator-checked).
save	Ability	required	The saving-throw ability every creature caught in the cone rolls.

NaturalAttack

One natural attack off a monster's stat block: a bite, claw, or slam the creature IS armed with — not a borrowed weapon. PRIMITIVES only: to-hit and the damage average DERIVE (pb_for_cr + the governing ability's mod), exactly as a humanoid's weapon line does. The ability names which mod feeds both (Str for a slam, Dex for a wolf's quick bite — the finesse rule made explicit for the raceless). reach_ft is the melee reach (5 ft on the grid = one square; a longer reach is ledgered); a ranged natural attack carries range (none in the starter bestiary — the substrate for a manticore's spikes, ledgered).

Field	Type	Required	Description
ability	Ability	required	The ability whose mod feeds to-hit and damage (Str, or Dex for a finesse-like bite).
damage	Damage	required	The attack's damage dice and kind.
name	string	required
range	Range	optional	Ranged natural-attack range; absent = melee only.
reach_ft	uint32	required	Melee reach in feet (5 ft = one grid square).

Range

Weapon-range band in feet.

Field	Type	Required	Description
long	uint32	required	Long range in feet — an attack beyond `normal` up to this is at disadvantage.
normal	uint32	required	Normal range in feet — no penalty within it.

Size

Creature size — the full SRD ladder (Tiny..Gargantuan). Races span Small/Medium; the bestiary's monsters reach the rest, and the hit die swings by it (combat::srd::hit_die).

TinySmallMediumLargeHugeGargantuan

Skill

The eighteen SRD skills.

AthleticsAcrobaticsSleightOfHandStealthArcanaHistoryInvestigationNatureReligionAnimalHandlingInsightMedicinePerceptionSurvivalDeceptionIntimidationPerformancePersuasion

Source

Every file's top-level value carries source.

`Srd51`

SRD 5.1 — the System Reference Document, the shipped baseline.

`Original`

Original content authored for this game (not from the SRD).

`Personal`

A player's own transcription or third-party content in a mod tree — provenance stays honest without borrowing the base tree's markers. Never used by shipped files.