Monster

Monsters are hostile Creatures that serve as sources of danger and conflict to your Gnomes. Setting the game to Peaceful Difficulty will disable monster spawns by default.

Monsters can break down Doors and tunnel through walls. The strength of the material determines how quickly this can be done. Originally, RoboB0B planned to have the quality of a door affect how long it took to break down, but this was never added into the game before development was abandoned. Doors will drop as an item when broken, allowing them to be picked back up and rebuilt.

There are three different spawning types for monsters: Invaders, Item Pile spawning, and Darkness spawning. Invaders will invade based on specific conditions, with Goblins and Ogres spawning based on the total value of your kingdom, and Mants spawning based on the total amount of food that your kingdom has.

Trivia

 * All Goblins and Ogres will have the same kingdom for the whole game, though this name is randomized per game.
 * This can include some rather questionable names, such as "Pissgrowl" and "Crucifixionmusic".
 * Mants have no kingdom.
 * Spiders are, according to the original wiki, the deadliest enemies in the game.