Imperial War Mastiff

"Mastiffs are the most common breed used by the Imperial Legions as battle dogs. The Imperial War Mastiff in particular is the mascot and symbol of the storied Second Legion, headquartered in peacetime in the vicinity of Bruma."

- In-game description

The Imperial War Mastiff is a pet dog in. It could only be obtained from Mysterious Reward Boxes earned during the 10 Million Stories dungeon event that lasted from between November 30th to December 6th.