Lost Island is an anime-only island that exists beneath Warship Island, underneath the water, and rises once every 1000 years. The inhabitants of Warship Island are said to have once lived here. The Sennenryu, a thought-to-be extinct race of dragons that live for 1000 years, were suspected at one point to live here, but are now scattered across the world. This is one of the locations of the Warship Island Arc.
However, there appears to be some inconsistency with what Lost Island is. If Lost Island is the ancestral island of the Warship Island's inhabitants, then it is located within a mirage and a storm. However, if it is to solely refer to the nesting grounds of the Sennenryu, then it is the underwater land surrounding Warship Island.
Lost Island is covered with dragons whose bodies have become calcified due to being underwater for thousands of years. There are many forms of ocean sealife such as coral present on the island developed from the extended amount of time it exists underwater.
Amongst his descendants was Pokeportes, who had 3 sons: Bokehontas, Bokebonboko, and Bokebokepon. Pokeportes sent them to find the tree that bears stars in the Valley of the Dragons. The three sons bravely set out to find this valley.
316th generation of Iscardunk's family bore Ingrimongri III, whose son, Ingrigrimori, the 317th generation and 316th descendant of Iscardunk was said to have become a great ruler. He had 18 sons.
Eventually, there was another descendent, King Ikemenes who had carried out many reforms. He had 65 sons, and so it was said that if one would throw a stone into the kingdom, you would hit one of the princes.
The 1,121st king was Hokehontas and afterwards, came Nemenememitas, who thought of a way to protect their kingdom from an attack from larger nations.
- One Piece Anime — Episode 55, Bokuden discusses the history of Lost Island.