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-Pointed 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-Pointed Star.

The Secret of the Wraiths
These dens are sites where the acolytes for the titular Order of the Wraiths have stationed themselves at. Alongside normal spelunking hijinks you also have to regularly fight these acolytes, and in the end you have to destroy their shrines after defeating the dens resident boss. The final den on this list can only be entered once the other dens on the list have been completed.

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.