Pikmin Evolution/Dens

Dens are subareas in Pikmin Evolution that are similar in concept to caves, as both involve taking a squad of Pikmin to explore a multi-layer location usually ending in a climactic fight. Each floor is limited in size and contains a predetermined set of hazards and enemies, with some dens being designed around a certain theme such as food or toys, or a certain type of enemy such as grub-dogs. Dens differ from caves in that, while some dens take the form of a downward cave that contains a fan leading back to the entrance, some take the form of vertical towers where the end goal becomes heading to the top of it and riding a balloon back to the bottom.

The 9-Pieced Star
These dens include the first den explored and generally act as introductions to the concept of spelunking. The end of each den has one of the pieces of the titular 9-Pieced Star.

The Secret of the Wraiths
These dens are sites where the acolytes for the titular Order of the Wraiths have stationed themselves. Alongside normal spelunking hijinks, fighting the resident acolytes is a necessity, and in the end, their shrines must be destroyed and their leaders slain. Melancholy Castle can only be entered once the other dens have been cleared.

Realm of the Beast Lords
These dens are the homes of the six great beast lords. Each den is themed around the habitat of their respective lord and features enemies that live in those habitats. At the end of each den is a battle against one of the six beast lords, which each drop a piece of a tablet relating to this planet's ancient history.