I've mentioned this over the past few days, but I think an awesome piece of endgame content to implement would be discovery missions. The way these could trigger would be if you were exploring a planet (e.g. Nessus) and you're in a specific area (e.g. Artifact's Edge) and you investigate certain things with your ghost in a specific order (so as to have some sort of side-story cohesion), then you activate that area's "discovery mission". There could be planet specific loot (legendary Nessus shader, legendary discovery emblem, maybe a discovery aura? etc...) What do you think guardians??