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Shadowthrall Parasite Brain

Based on game build 714014 | Last updated: 2026-02-27

Overview​

This brain component defines the behavior tree for the shadowthrall parasite entity in Don't Starve Together. Its primary responsibility is to manage simple evasion logic: the parasite continuously moves away from nearby players or shadow rift portals, and automatically destroys itself if no players are within a given detection radius. It extends Brain and uses standard DST behavior tree patterns, incorporating the RunAway and DoAction behavior nodes to implement its logic. The component does not directly interact with other components but relies on global utility functions like IsAnyPlayerInRange, FindClosestPlayerToInst, and TheSim:FindEntities.

Usage example​

This component is not intended to be manually added or invoked by modders. It is automatically attached to the appropriate entity via the game’s prefab definition. A typical usage pattern inside the prefab file would look like:

inst:AddBrain("shadowthrall_parasite_brain")

Dependencies & tags​

Components used: None identified. Tags: shadowrift_portal (used in entity tag filtering via TheSim:FindEntities)

Properties​

No public properties are defined in the constructor or outside it. All state is managed through the behavior tree and local functions.

Main functions​

ShadowThrall_Parasite_Brain:OnStart()​

  • Description: Initializes the entity’s behavior tree at brain startup. Sets up a priority node that evaluates two behaviors: first checking if the entity should be removed (via TestForRemove), and second, initiating flee movement toward a safe distance from the closest threat (via RunAway).
  • Parameters: None.
  • Returns: nil.
  • Error states: None documented; assumes valid inst and proper behavior node definitions.

TestForRemove(inst)​

  • Description: A standalone utility function used in the behavior tree. Checks whether any player is within the camera’s see distance (PLAYER_CAMERA_SEE_DISTANCE). If no players are nearby, it removes the entity from the world.
  • Parameters:
    • inst (Entity): The parasite entity being tested for removal.
  • Returns: nil.
  • Error states: May silently do nothing if the entity is not currently owned or its transform is invalid.

GetRunAwayTarget(inst)​

  • Description: A standalone utility function used by the RunAway behavior to determine the nearest threat. It prioritizes a player if one is nearby (within PLAYER_CAMERA_SEE_DISTANCE), otherwise falls back to the first nearby shadow rift portal.
  • Parameters:
    • inst (Entity): The parasite entity requesting a target.
  • Returns: Entity — the closest player or shadow rift portal, or nil if none found.
  • Error states: May return nil if no players and no rift portals are found in the search radius.

Events & listeners​

None. This brain does not register or fire events. Behavior updates are driven by the behavior tree evaluation loop.