Marvel Heroes 2015 end-game players will want to check out the new game mode called "The Danger Room". The Danger Room is an event that will feel different each time it is run due to randomized levels, missions, bosses, hazards and modifiers. A special item dropped called a Danger Room Scenario can be used to create instanced, multi-stage simulations.
A specific hub for the Danger Room has been created that also features a new crafter, vendor and has powers enabled. Each party will see their own version of the hub and can only be reached by players of level 60.
You can find out more about Danger Room by reading the handy FAQ on the Marvel Heroes 2015 forum.