The trap is a Misc Structure that acts as an automated defense/source of damage.
The trap's default state is unarmed, and can be armed immediately, by interacting with it. The trap cannot be disarmed manually and remains armed until an entity (passive creature, enemy or player) moves into the trap's range, immediately above it. If a player tries to reset the trap too soon after being triggered, a message will display, "Troll trap is not ready yet."
Caution is advised when setting/arming traps, as they can kill the player.
