The Military Cruiser is an ultimate introduced in the 13.0.0 update.
It appears to be a large, mainly blue (and red on the bottom) ship with various barreled guns and turrets on it.
It bombards the battlefield with large-caliber guns.
At this moment, ultimates like this are not in the game. It is expected that ultimates will be added to the game at some point due to the fact that the player is able to browse them in the clan fort section, and also in the clan storage, which is quite misleading. At the moment, it is unsure if an ultimate will be an ability used once per game, or if it will be constant.