Forgotten beast

Forgotten beasts are large, monstrous, procedurally generated megabeasts that spawn in the caverns beneath your fortress, pathing through to your fort and seeding destruction amongst your dwarves. They are the subterranean equivalent of titans.

Forgotten beasts are attracted by wealth and population size. They start coming from breached caverns once the population reaches 20. Additionally, one may randomly appear when you reclaim a fortress. When a forgotten beast becomes visible onscreen, the game automatically pauses and displays a message.