The Terminal is part of an old rail line that was under the post office. With the post office being brought back online as The Base of Operations during the second wave activation of agents. It was a logical step to use the rail line as a means to get around to city to act quickly on situations as they unfold.
Dragon's Nest is an Incursion for The Division released in Update 1.3. The Joint Task Force [JTF] are investigating amassing of Cleaner forces in the Port Control Transit Terminal. A squad of Division agents join the investigation and ultimately uncover the Cleaners' new secret weapon: a fire truck mounted with a flamethrower and incendiary mortar launcher, christened the "Dragon." The agents must destroy "Dragon One" before it ever sees the light of day and wreaks havoc upon New York City.
Also, Chris Radsby as he assisted and helped me finish out some of the starting areas so I could focus on the rooftop encounter.