In Story of Seasons, agate might be needed to complete certain quests or trade with specific characters for valuable rewards. Also, it could be used as a material for upgrading tools or buildings.
In << Mortal Cultivation Biography >>, agate horn was a rare material for refining weapons. It could be used to refine magic weapons. Agate horns could be obtained by killing demon creatures or in some special places, such as some mysterious caves or ancient tombs.
While waiting for the TV series, he could also click on the link below to read the classic original work of " The Legend of Mortal Cultivation "!