Black flowers are a type of flower that can be harvested after planting Mithril seeds, which are purchasable from the Gambler NPC at the gambling area. When planting the mithril seeds, players have an option to either pick the flowers or leave them planted on the ground. A player only has one chance to pick their flowers; if they refuse to do so, they will not get the option again unless they plant another mithril seed. Black flowers have a 1/100,000 chance of spawn from mithril seeds.
