A behavior controller system and its operations are described herein. In embodiments, the operations can include detecting one or more events that occur within a wagering game. The wagering game can feature a wagering game object that can automatically (e.g., intelligently) respond to the one or more events. The behavior controller system can use event-driven behavior controllers, such as a behavior tree. The behavior controller system can determine, and activate, tasks on the behavior tree that cause the wagering game object to respond to the one or more events. In some embodiments, the behavior controller system can also prioritize tasks that may be performed by behavior trees to prevent conflicts between wagering game objects during a wagering game.