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Crabkingbrain

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

Overview​

Crabkingbrain implements the boss AI logic for the Crab King entity in DST. It uses a behavior tree (BT) to orchestrate high-priority actions such as healing, casting claws, freezing, and cannon fire, triggered conditionally based on the entity's state, health, and surroundings. The brain integrates with components like health, timer, knownlocations, and combat, and depends on external behavior modules like doaction, panic, and wander. It does not override standard Brain lifecycle methods beyond OnStart and OnInitializationComplete.

Usage example​

This brain is attached automatically to the Crab King prefab during entity initialization. Modders typically do not instantiate it directly but can inspect or override its behavior tree by hooking into the entity's state graph or behavior setup.

-- Example: Attaching the brain to a custom boss entity (conceptual only)
local inst = CreateEntity()
inst:AddComponent("brain")
inst:AddComponent("health")
inst:AddComponent("combat")
inst:AddComponent("timer")
inst:AddComponent("knownlocations")
inst:AddTag("monster")
inst:AddTag("icewall")
inst.components.brain = CrabkingBrain(inst)
inst.components.brain:OnStart()

Dependencies & tags​

Components used:

  • combat (target property referenced)
  • freezable (IsFrozen called)
  • health (GetPercent called)
  • knownlocations (RememberLocation called)
  • timer (TimerExists called)

Tags:

  • character, animal, monster, smallcreature — used in TheSim:FindEntities filtering for valid targets.
  • icewall, boat, boat_ice — used to conditionally gate actions (e.g., freezing, healing).
  • No tags are added/removed directly by this brain.

Properties​

No public properties are initialized in this brain. All state is managed internally or via attached components.

Main functions​

OnStart()​

  • Description: Initializes the behavior tree (bt) with a priority-based root node. The root evaluates high-priority actions (heal, freeze, claws?) in sequence, but only if the entity is not in inert, casting, fixing, or spawning state tags.
  • Parameters: None.
  • Returns: Nothing.
  • Error states: None identified; assumes required components and state graph tags exist.

OnInitializationComplete()​

  • Description: Records the Crab King's starting position as "spawnpoint" in the knownlocations component for future reference (e.g., retreat or teleport logic).
  • Parameters: None.
  • Returns: Nothing.

Events & listeners​

None identified — this brain does not register event listeners or push custom events. All decision logic resides in the behavior tree preconditions (ShouldHeal, ShouldFreeze, etc.).

Note: Functions like ShouldHeal, ShouldFreeze, ShouldHaveClaws, and ShouldCannon are helpers used by DoAction behavior nodes. They are not exposed as brain methods but define the conditions under which actions execute. ShouldCannon is referenced in the file but not used in the current behavior tree root.