DA_RareEvent — Rare Event Data Asset

Blueprint Spec — UE 5.5–5.7

Parent Class

UPrimaryDataAsset

Dependencies

Requires: GameplayTags — EventTag, EventConditions, EventActions
Required By: BPC_RareEventSystem — Reads rare event pool at runtime, rolls probability, fires events
Engine/Plugin Requirements: GameplayTags

Purpose

Defines a single rare world event that can occur with limited probability during gameplay. Each rare event asset specifies its unique tag, probability of occurrence, eligibility conditions, resulting actions, and whether it can fire only once per session.

1. Enums

Enum Name: E_RareEventActionType
(DisplayName = "Rare Event Action Type")

Values:
  PlayAudio              = 0    // Play a one-shot sound or stinger
  SpawnActor             = 1    // Spawn a visual/hallucination actor
  TriggerScreenEffect    = 2    // Trigger a screen effect (vignette, flash)
  SetNarrativeFlag       = 3    // Set a narrative flag
  TriggerDialogue        = 4    // Play a dialogue line or sequence
  ModifyAtmosphere       = 5    // Temporarily change atmosphere state
  SpawnCollectible       = 6    // Spawn a hidden collectible
  DisplayMessage         = 7    // Show a subtitle/message to player
  ModifyLighting         = 8    // Change room lighting temporarily
  TeleportEntity         = 9    // Teleport an entity near player briefly

2. Structs

`S_RareEventAction`

Field	Type	Description
`ActionType`	E_RareEventActionType	What kind of action to perform
`ActionTag`	GameplayTag	Action-specific identifier (audio cue, actor class, effect tag)
`ActionValue`	Float	Numeric parameter (duration, intensity, volume)
`Delay`	Float	Seconds to wait before executing this action

3. Variables

Data Asset Fields

Variable	Type	Default	Category	Description
`EventTag`	GameplayTag	—	Identity	Unique identifier for this rare event
`DisplayName`	FText	—	Editor	Human-readable name for designers
`Probability`	Float	0.01	Core	Chance of occurring on each roll (0.0–1.0)
`EventConditions`	Array of GameplayTag	Empty	Conditions	Narrative flags required for event to be eligible
`ForbiddenConditions`	Array of GameplayTag	Empty	Conditions	Narrative flags that block the event if set
`EventActions`	Array of S_RareEventAction	Empty	Actions	Sequence of actions executed when event fires
`bOncePerSession`	Bool	True	Core	If true, event fires at most once per game session
`bOncePerSaveFile`	Bool	False	Core	If true, event fires at most once per save file lifetime
`bBlockOtherEvents`	Bool	False	Core	No other rare events can fire during this event's action sequence
`RequiredPlaystyleTag`	GameplayTag	—	Conditions	Player must have this playstyle for eligibility
`RequiredChapterTag`	GameplayTag	—	Conditions	Current chapter must match for eligibility
`MinSessionTime`	Float	0.0	Conditions	Minimum session elapsed time before eligible
`MinDeathCount`	Integer	0	Conditions	Minimum player deaths before eligible
`MaxOccurrences`	Integer	1	Limits	Maximum times event can occur (overrides bOncePerSession)
`CooldownAfterFire`	Float	0.0	Limits	Cooldown in seconds before this event is eligible again
`Priority`	Integer	0	Core	Priority over other events when multiple are eligible (higher = first)

4. Functions

Data asset only. No runtime functions. Data is read by BPC_RareEventSystem at runtime.

5. Event Dispatchers

Data asset only. No event dispatchers.

6. Validation / Testing Checklist

EventTag is unique and valid GameplayTag
Probability is in range 0.0–1.0 (0.001 = 0.1%, 0.01 = 1%, 0.1 = 10%)
EventConditions tags exist in GI_GameTagRegistry
EventActions array has at least one action
S_RareEventAction.ActionType matches the data needed (audio uses ActionTag for cue, spawn uses ActionTag for actor class)
bOncePerSession and bOncePerSaveFile properly gated (don't set both unless intended)
Priority values correctly order competing events
Edge case: Probability of 0.0 = never fires randomly (scripted only)
Edge case: Probability of 1.0 = always fires when eligible
Edge case: empty EventConditions = always eligible
Edge case: CooldownAfterFire of 0 = no cooldown (only gated by bOncePerSession/MaxOccurrences)

7. Example Data Row

Field	Value	Note
`EventTag`	`RareEvent.Hallucination.CorridorGhost`	Unique identifier
`DisplayName`	"Corridor Ghost Sighting"	Designer reference name
`Probability`	0.005	0.5% chance per roll
`EventConditions`	[Narrative.Phase.Ch2, Player.Stress.High]	Only in chapter 2 when stress is high
`ForbiddenConditions`	[Narrative.Flag.SeenGhost]	Doesn't repeat if already seen
`EventActions`	[SpawnActor(GhostMesh, 0.5, 0.0), TriggerScreenEffect(Flash, 0.3, 0.5), PlayAudio(GhostWhisper, 0.8, 1.0)]	Three sequential actions
`bOncePerSession`	True	Don't repeat
`bOncePerSaveFile`	False	Can appear in different save files
`RequiredPlaystyleTag`	Cautious	Prefer scaring cautious players
`RequiredChapterTag`	Narrative.Phase.Ch2	Only in chapter 2
`MinSessionTime`	600.0	At least 10 minutes played
`MinDeathCount`	2	Player must have died at least twice
`Priority`	5	Higher than ambient events, lower than story reveals

8. Reuse Notes

One DA_RareEvent per rare world occurrence
Probability values should be very low (0.001–0.05) for true "rare" feel
EventActions array supports complex multi-step sequences with delays
bBlockOtherEvents prevents simultaneous rare events from stacking
For non-horror games, use rare events for easter eggs and hidden content instead of scares
Extend E_RareEventActionType with new action types per project
CooldownAfterFire allows events to repeat within a session without being once-only

Specification based on Master Section 13, line 3422.

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