From the Super Mario Wiki
Gloam Valley is the setting of Chapter 2 in Super Paper Mario. The valley itself only appears in the first section of the chapter.
 Chapter 2-1: Bogging to Merlee's
After finding the tower of the Orange Pure Heart in the Flipside Outskirts, Mario and his friends access Gloam Valley through an Orange Door. The Gloam Valley is in a state of perpetual sunset with many wind turbines in the background. There is an abundance of tall foliage and many enemies. There is also a swamp Princess Peach has to glide over with her parasol, because Mario is unable to glide.
Near the end of the swamp, Mario meets Boomer. Boomer gives Mario a quiz, which is always won no matter which answers the player chooses. Overjoyed, Boomer joins Mario.
A person named Lock can be found in Gloam Valley. If any characters other than Princess Peach try to talk to him, he insults them and tell them to go away. However, he is in love with Peach when he sees her.
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