Rules of the Underground Onion

In Pikmin 4: the wraith's revenge, In certain Dungeons the Onion/Onions will follow you into that dungeon. This occurs in:
 * Very Challenging Dungeons (Appearing on the most challenging floors)
 * Introductory Dungeons (Only the Dungeon's introduced Onion)
 * Boss Floors (Halfway through the game)

In the case of Challenging Dungeons, you can bring out 150 more Pikmin if yours all died. In the case of Boss Floors, you can bring out 50 Pikmin In the case of introductory Dungeons, you can bring out 10 Pikmin. In the introductory dungeons, you mostly just bring them to grow your Pikmin amounts.