Alongside the new field, Axion Plains, The First Descendant introduced the largest Colossus intercept battle yet. Wall Crasher intercept battle is an eight-player event you can participate in to try and get a bunch of rewards, including the new Trigger Modules.
Wall Crasher appears every hour on the hour (at 00 minutes) in Axion Plains, and you must enter the fight within five minutes by approaching the central structure in the field. This puts you into matchmaking and loads you into an instance with seven other players.
