CSS La Sirena
CSS La Sirena (NCC-93131) was a Kaplan F17 Patrol Frigate that served the Confederation of Earth under the command of Colonel Cristóbal Rios during the early 25th century.

History
In 2401, the CSS La Sirena and several other patrol frigates were involved in an attack on Vulcan forces in orbit of . Transported from his reality by Q, Captain Cristóbal Rios suddenly found himself aboard this ship in the middle of battle, just in time to see Confederation forces bombarded the planet. ()

La Sirena was subsequently recalled to Earth by Seven of Nine under the guise of Confederate President Annika Hansen. Seven, Rios, and the other associates of Jean-Luc Picard, whom Q stranded in this alternate reality, decided to use La Sirena to return to the past and fix the timeline. They kidnapped the captive Borg Queen and convinced her to help them perform a slingshot maneuver around the sun to travel back in time to 2024. To give the Borg Queen access to the ship's systems and allow her to make the necessary calculations, Dr. Agnes Jurati physically plugged the Queen into Sirenas systems, through data cables from the ship's main array. ()

As they were flying towards the sun, La Sirena came under heavy fire from pursuing Confederation starships. This, in combination with the damage incurred through the slingshot maneuver, drained the ship's systems, to the point where it got caught in Earth's atmosphere. Rios was only able to restore 39% navigational control, which sufficed for a controlled crash landing near Château Picard. ()

The Borg Queen continued to drain power from the ship's systems, shutting down the biobed in sickbay that was keeping the injured Elnor alive. When the crew could not disconnect the Queen and decided against killing her, since that would destroy their only chance to restore the timeline and get home, Elnor died of his injuries. Raffi laid his body in one of the ship's two stasis chambers in the wall of sickbay.

Over the next few days, as they tried to fix the change to the timeline caused by Q, the crew of La Sirena also fought a continuous battle for control of the ship against the Borg Queen and the malicious code and system lockouts she injected into the ship's computer. While Picard and the others needed the ship to return to their own time, the Borg Queen hoped to take control of La Sirena to travel to the Delta Quadrant and begin establishing the Borg Collective long before it was supposed to exist in this timeline. () 

Eventually, after assimilating Jurati and taking over her body, the Borg Queen was able to gain full control of the ship. To save her friends' lives, Jurati convinced the Queen that she should not assimilate them, but that they should form a new, voluntary Borg Collective. As payment for saving Seven of Nine's life, the new Queen demanded control of La Sirena. She took off from Earth on April 15th 2024, hours before the launch of the Europa Mission. ()

In addition to Agnes Jurati's body, now inhabited by a merged consciousness of Jurati and the Borg Queen, the ship had the old body of the Borg Queen, as well as Elnor's corpse on board as it took off. ()

Technical data
The main body of the ship was comprised of two decks. While the bridge, living quarters, transporter, and main engine access were found on the upper deck, the lower deck held the mess and sickbay. Various containers of weapons and explosives were stored around the upper deck, while crates of medical supplies filled sickbay.

While the bridge consoles and transporter console were equipped with touch screens, the bridge also had holographic controls, and the piloting control was entirely holographic.

La Sirenas sickbay was equipped with a biobed as well as two stasis chambers. ()

To avoid detection while on Earth, Picard concealed the ship using the Confederation-issue cloaking device. However, whether due to malfunction, limited power, or the fact it was designed to function in outer space, the cloak was imperfect and allowed people on the ground to partially see the ship, even at night. ()

The CSS La Sirena was equipped with holo-emitters throughout both main decks as well as sickbay and the living quarters. It also possessed a system that could create a hologram from any person who had ever been on board. Agnes Jurati used this system in the final hours of her struggle with the Borg Queen in 2024, to create an Emergency Combat Hologram based on Elnor. This ECH was able to harm and kill the Borg soldiers who had infiltrated the ship, and he retained many of Elnor's memories, including his last thoughts before dying. The newly created ECH had a mobile emitter pinned to his upper arm, but it was apparently holographic itself, rather than replicated, and might not have been functional.  ()

In addition to large cargo doors at the back of the ship, La Sirena could be accessed through an access hatch on the starboard side of the lower deck. ()

Appendices

Appearances
 (Season 2)

Background 
In season 1, when the prime timeline's La Sirena crashes on Coppelius, the ship gets buried deep enough that the ground outside becomes level with the panorama window, which spans the ship's upper and lower decks. This means the crew can use the window as an entrance and exit, but it is very much an improvised, non-permanent solution. This is evidenced by the three foot drop just inside the window, which had to be bridged by planks, and the lack of any door or hatch. ("La Sirena Set Tour", ; ) On the CSS La Sirena, on the other hand, changes to the floor plating suggest that the gap to the starboard bulkhead of the lower deck is permanently closed, and from context it appears there might be a fully functional access there, including a pneumatic door or hatch. )

Confederation starships