The 4th add-on included in the season pass for ACE COMBAT™ 7: SKIES UNKNOWN. This add-on allows you to play the new mission "Unexpected Visitor." SP MISSION 01: Unexpected Visitor A giant Erusean submarine has been discovered in harbor at Artiglio Port. This submarine launched four years ago, but went missing during a sea trial. It was found two years later at the bottom of the ocean. Much of its crew survived and were rescued. According to David North, an analyst from the Osean Intelligence Agency's Advanced Weapons Analysis Division, this submarine is a super-sized nuclear submarine measuring 495 meters in length and powered by two liquid metal cooled reactors. Dubbed the "Alicorn," it is capable of staging aircraft operations on the scale of a carrier. The objective of this operation is to capture the Alicorn. To do so, the Osean Navy has dispatched a fleet complete with a landing ship. "Our mission is to secure air superiority and protect this assault-and-capture task force."