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Shadowthrall Parasite Brain

Based on game build 714014 | Last updated: 2026-03-03

Overview​

ShadowThrall_Parasite_Brain is a behavior tree-based AI component for shadow thrall parasites. Its primary responsibility is to manage the entity's lifecycle and movement in response to environmental conditions: it schedules the entity for removal if no players are within viewing distance, and forces it to flee from the nearest player or nearest shadow rift portal if either is present. This component inherits from Brain and uses the behavior tree (BT) system to coordinate its logic.

The component relies on external behavior modules (follow, wander, standstill, faceentity) and utility functions (FindClosestPlayerToInst, IsAnyPlayerInRange, TheSim:FindEntities) to implement its decision-making.

Usage example​

local inst = CreateEntity()
inst:AddTag("shadowthrall_parasite")
inst:AddBrain("shadowthrall_parasite_brain")

Dependencies & tags​

Components used: None identified
Tags: Checks for shadowrift_portal via entity tags during search.

Properties​

No public properties

Main functions​

OnStart()​

  • Description: Initializes the behavior tree. Sets up a priority root node that first evaluates whether the entity should be removed, and if not, activates a RunAway behavior targeting the closest player or nearest shadow rift portal.
  • Parameters: None.
  • Returns: Nothing.
  • Error states: None — always sets up a new behavior tree with a fixed root node.

Events & listeners​

Not applicable

Helper Functions​

TestForRemove(inst)​

  • Description: Checks if any player is currently in range (within PLAYER_CAMERA_SEE_DISTANCE). If not, schedules the entity for removal via inst:Remove().
  • Parameters: inst (entity instance) — the entity being tested.
  • Returns: Nothing.

GetRunAwayTarget(inst)​

  • Description: Determines the appropriate target to flee from. First attempts to find the closest player; if none found, searches for the nearest entity tagged with shadowrift_portal.
  • Parameters: inst (entity instance) — the entity computing the target.
  • Returns: Entity instance or nil — the nearest player or shadow rift portal, whichever exists and is closer.
  • Error states: Returns nil if no players and no shadow rift portals are within PLAYER_CAMERA_SEE_DISTANCE.