It is one of the locations that were in the beta and the names were changed in the official launch of the game. but some of the quest still call them from the beta name for some reasons. The Forgotten Monolith was in beta and now it is called Forsaken Monolith
"In Once Human, what was known as the Forgotten Monolith in the beta is now called the Forsaken Monolith and is located in the western area of the Red Sands region."