Mislay Triangle

The Mislay Triangle is an optional location in EarthBound Beginnings, which lies to the north of Reindeer. A man who is rumored to haven't had a single cold in 300 years lives in a building there.

Layout
The Mislay Triangle is accessed from an opening north of Reindeer and west of the train tracks. A large building is located in the center on the hilltop where an old man lives. East of the building is a slope which leads to a path that loops around the hill the building is on in a counterclockwise direction. At the end is a sign where the old man's dentures are found.

In EarthBound Beginnings
When Ninten meets the old man for the first time, he talks incomprehensively. However, beneath a sign, which can be reached by walking counterclockwise around the building, his dentures can be found, and must be returned to him in order to make him able to speak coherently again. He will reward Ninten by telling him the secret to his immunity to colds, which is revealed to be thanks to the use of Mouthwash. He then fills the remaining space of Ninten's and his friends' inventories with Mouthwash for free. A young boy, who also resides in the building, will from that point and on sell Mouthwash for $10 each.

Trivia

 * Obtaining Mouthwash from here and selling it can be used as an effective way to earn money, as the boy only charges $10 for one and Mouthwash can be sold for $87 each in most stores.