During "My Name is Cyrus Temple" only
The Thermopylae is present in the water to the east of Port Pryor after STAG's appearance in Steelport. While it is shown during a cutscene during that mission, the view during the cutscene is impossible and the carrier itself is not present until the mission has been completed.
Its appearance signals the first deployment of STAG troops into the city.
About two-thirds into Saints Row: The Third, Shaundi is kidnapped by Kia and taken prisoner aboard the Thermopylae.
The Protagonist infiltrates the ship while disguised as Cyrus Temple and using Pierce and Viola as prisoners. The mission takes place in a normally inaccessible interior, which includes the bridge, a brig and a hangar bay. After his cover is blown, The Protagonist sabotages the Thermopylae's reactor and escapes via a VTOL transport. The massive warship explodes, splitting in half and partially sinking in the waters of Steelport.
The Thermopylae is a massive aircraft carrier loaded with advanced military hardware, primarily carrying F-69 VTOLs and Condor transports, along with a substantial complement of STAG troops; she also carries the STAG prefabricated bases, tanks and light vehicles which are deployed around Steelport, though it is not clear how these are transported or what by. The vessel is Cyrus Temple's mobile command centre, and it is implied the entire STAG force in Steelport was deployed from the Thermopylae.
While they have no impact on gameplay, the Thermopylae also has a substantial number of missile batteries located along her flanks and two large triple launchers on the bow.
The carrier is an unusual design with a forward-facing, partly covered launch deck and covered hangars under a pair of short-take-off strips; behind these is a small secondary island or forward control tower. Behind this is a slanted recovery deck with two helipads on one side and a massive elevator on the other. The carrier's main island and radar tower are located astern. The long strips at the bow and recovery deck imply the Thermopylae is designed to launch CATOBAR aircraft. Throughout the game, the Thermopylae only carries F-69's. It also lack the catapult and arresting equipment of a CATOBAR carrier which means it's most likely can only operate V/STOL aircrafts like the Condor or F-69.
The interior of the Thermopylae is composed of multiple rooms:
- Research and Development
- A large computer room with three main entrances and a small hallway on the left side. The hallway has another door that leads to the Hangar room and a small entrance that leads to the upper room containing the computer with access to the "S.T.A.G. Prototypes".
- Loading Bay
- A large bay where STAG supplies are stored. There's a large unusable cargo door located down a ramp on the room. There are large brown crates, small STAG boxes and three Crusaders stored on the room. There are hallways on both sides of the room, and down the main ramp, with the lower left hallway leading to the Brig.
- A large room that contains a security room and where the cell blocks are located. The cell blocks have two levels, with steel platforms and stairs leading to the upper level cell blocks.
- Reactor Control Room
- This is where the Thermopylae's main engine is located. On the bottom, there's a console room section used to control the engine's functions and temperature.
- Hangar Room
- A large storage room where STAG aircraft are stored. This room is surrounded by large doors and a large aircraft elevator to take an aircraft to the Thermopylae's exterior.
- The Battle of Thermopylae was a battle between allied Greece city-states against the invading army of Persia.
- The Thermopylae is always empty outside missions, with no personnel or aircraft visible on the deck. Some STAG troops spawn due to Notoriety.
- There is a Builder's Plaque at the end of the runway, which reads "STAG carrier 001", "Surrender not unto thine enemy", "SJRT 150307", "HJF 210910", "Constructed under Volition, Champaign Shipyards, IL".
- Approaching the Thermopylae outside the mission "My Name is Cyrus Temple" triggers an instant level 5 police Notoriety. Approaching the wreck after the mission incurs no Notoriety.
- After the mission "My Name is Cyrus Temple", it is half sunken in the same location.
- Falling through the map shows the sunken Thermopylae is actually two complete Thermopylae models, one for each half, however both have visible damage to their superstructure unlike the original model, and are missing features such as the builders plaque.
- The Thermopylae has a big ID number on the top of her island - "01" and the Daedalus has a similar large "02".
- The number on Thermopylae's main runway is "00", this may be an orientation aid for pilots taxiing to the takeoff point, as the so called zeroes are completely rectangular, unlike actual stencil type numbers.
- Following the sinking of the Thermopylae, Jane Valderama states in a breaking newscast that casualties were surprisingly light, but also refers to her newscast as "military approved news".
- The newscast also reveals that the carrier is nuclear powered like all modern US supercarriers.
- The cutscene showing the Thermopylae sinking is reminiscent of the sinking of the real life Titanic.