|This article is about the current version of DF.|
Semi-megabeasts are large and dangerous enemies that are similar to but smaller than regular megabeasts. In fortress mode, semi-megabeasts are attracted by the wealth of your fortress, and will not appear until a certain population size has been reached. When a semi-megabeast appears, the game will pause and display a notification of its arrival.
|This article or section contains minor spoilers. You may want to avoid reading it.|
Semi-megabeasts can arrive at your fortress when the population reaches 50 (this includes any children), 5,000 exported wealth, and 50,000 created wealth. Because wealth increases the number of Dwarves which arrive during migrant waves, creating lots of wealth early on in the game, i.e. making and trading steel items (which can create lots of wealth in a hurry), can result in semi-megabeasts arriving during the fortress' third -- or even second -- year, especially if their quality is high. As a result, make sure that you're making useful things out of your valuable materials, and don't use all your weapons-grade metals for making valuable furniture until you've got at least a few weapons and a militia.
If you do not want semi-megabeasts arriving, don't create unnecessary wealth until you're ready for them.