Follow that cloud and loot that treasure.
Sea of Thieves features a lot of randomly-generated world events, but some of the most significant have to be Skeleton Forts. Skeleton Forts are lairs that appears throughout the world, where players can find challenging combat and treasure. If you see a massive skull-shaped cloud on the horizon, follow it and it will eventually lead to a Skeleton Fort. These areas are swarming with foes, so don’t expect to take them all on your own if you wish to succeed.
There is much more loot found in the Treasure Room of the Skeleton Fort than you can carry. This means that after you’ve destroyed all enemies, you might have to contend with other players for the best items. The threat doesn’t end with killing the Skeleton Captain.