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 gained access to the Gloam Swamp through the Orange Door. The Gloam Swamp in a state of perpetual sunset with many wind turbines in the background. There is an abundance of tall foliage and many enemies. Princess Peach proved her value in the party in the swamp; without her, Mario could not have gone through as he does not have the ability to glide over long distances.
Near the end of the swamp, Mario met the bomb Pixl, Boomer. Boomer gave Mario a quiz, which is always won no matter which answers the player chooses. Overjoyed, Boomer didn't hesitate to join Mario on his quest. Boomer proved very useful, and destroyed the blocks that were at the time preventing their passage.
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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