Enemies scale their difficulty the longer you are in a mission (similar to mythic+ dungeons, without having to requeue). Lots of people play this as “Endurance” content. Where they stay in missions longer to see how long they can survive. Example; https://www.youtube.com/results?search_query=endurance+warframe Great way to pair up resource farming, or relic farming (getting relics/loot boxes as rewards to then open later).
Survival, Defense, Interception, and Excavation:
Rewards for this kind of content:
Platinum (getting shit other players want to buy)