There is a wide variety of powerful weapons in Beast of Reincarnation, and Crescent Moon is one of the most useful ones. To obtain the Crescent Moon, go to the teleport point at Cableway Station 0 in the Giant Tree area of the Sunken Region. From there, head to a nearby high-rise building and speak with the Overlord Golem to receive the Crescent Moon.
How to Obtain the Crescent Moon Weapon in Beast of Reincarnation