Lost Sectors are a location on the Planetary Map that are hidden caches of engrams.
Lost Sectors are mini-dungeons that feature a unique boss within that guards a cache of gear. Each will be hand-crafted and defeating the boss within will drop the key needed to open the cache at the end of it. These will scale up with player's levels.
It is unclear if they will be public or instanced for a fire team.
Known Lost Sectors