In Lost Ark, Unknown Island is an Adventure Island that you can only access at certain times of the day. You can find the island in the Sea of Heavens between the continents of Shushire and Feiton. On this island, you can find a total of three Mokoko Seeds.
When discovered, these seeds are dark green in color but then glow a bright yellow/green. Check out where you can find all three Mokoko Seeds on Unknown Island below.
Once you arrive at the island, you will fight against either the Beast King of Darkness or Beast King of Light to receive rewards. As you search for the island bosses, you'll come across these three Mokoko Seeds buried within the trees and foliage. We outlined exactly where you can find them on the map below.
Once you've discovered these seeds, you'll be closer to obtaining all 49 Mokoko Seeds located in the North Porycon Sea.
For more information on Lost Ark, check out All Mokoko Seed locations on Azure Wind Island in Lost Ark in Lost Ark and All World Bosses Locations in Lost Ark on Pro Game Guides.