While combating Borg incursions, the Federation, Klingon Empire and Romulan Republic discover that the Borg have been successful in assimilating an Undine. While the spread of this technique is prevented, this leads to them entering Fluidic Space to remove the Borg presence there. While in Fluidic Space, they discover the conflict between them and the Undine is being orchestrated by the Iconians. Fake duplicates of Alpha/Beta Quadrant ships attack Fluidic Space making it appear as though the Federation and other powers are attacking them.
The Federation and Klingon Empire assist the Romulan Republic in establishing their new homeworld on New Romulus. However during their research, and attempts to combat Tholian activity, they uncover an Iconian gateway beneath the surface. The gateway is activated and the actions of the powers inadvertently reactivate the entire Iconian gateway network.
Via a newly revealed ship-sized gateway in the Jouret System, the three powers gain access to the Solanae Dyson Sphere on the edge of the Delta Quadrant. It is discovered that the sphere uses mass amounts of Omega Particles in order to jump anywhere in subspace. The three powers form the Dyson Joint Command to disable the sphere's transwarp capabilities. This however brings them into conflict with the Voth.
While the powers succeed in their aim, they end up activating a gateway to the Jenolan Dyson Sphere. The Jenolan sphere itself jumped from the Beta Quadrant to the heart of the Delta Quadrant. This gives the powers access to the Delta Quadrant but brings them into closer conflict with the Undine and raises tensions between them.
To resolve the differences between the three powers, and counter the Undine, Rear Admiral Tuvok calls for a summit of Alpha and Beta Quadrant powers in the Jenolan Dyson Sphere. During this summit, the Undine launch an attack on Earth Space Dock and Qo'noS. After Qo'noS is saved by Federation Captain Va'Kel Shon, the three powers celebrate in the First City of Qo'noS. The celebrations are disrupted by the Iconian M'Tara who kills much of the High Council. The Federation and Klingon Empire subsequently agree to a cease-fire, ending the Federation-Klingon War and form the Alliance with the Romulans.
Delta Quadrant exploration
Using the Jenolan Dyson Sphere as their vantage point, the three powers explore the Delta Quadrant. While they identify several friendly and hostile species, they quickly discovered that the Vaadwaur Supremacy has now become a powerful military force. To combat the Vaadwaur's threat to the Quadrant, the three powers form the Delta Alliance with local friendly species.
One notable front is an ongoing campaign on Kobali Prime. During this campaign, it is discovered that high ranking Vaadwaur are being controlled by the Bluegill parasite and are acting as servitors of the Iconians. The Vaadwaur are eventually defeated with the combined aid of the three major powers and their Delta Quadrant allies.
Former Empress Sela of the Romulan Star Empire is discovered on an Elachi subspace outpost, having gone missing during the Reman attack on Brea III the year before. She reveals that the Elachi and Solanae serve as respective soldier and scientist castes for the Iconians. She later escapes from Romulan Republic custody and shows the Alpha/Beta Quadrant powers the might of the Iconians and their Herald-elite soldiers, who are gathering within the Andromeda Dyson Sphere.
The Iconian War begins when the Andromeda Dyson Sphere jumps to the Iconia System and the Iconians send their Heralds to attack various locations including New Romulus and Qo'noS. In a desperate attempt to prevent their destruction, the Alliance joins forces with the Krenim. The Krenim build a timeship, the K.I.V. Annorax, in the hopes of changing the timeline to avert the Iconian conflict.
In June, initial attempts to change the timeline result in the assimilation of Romulus. Attempting to correct the problem, the Alliance restores most of the original timeline but end up wiping out the Tuterians.
The final battle of the Iconian War takes place in the Sol System; the Dominion joins the battle on the side of the Alliance but are unable to turn the tide. The battle buys the Alliance time to send their ship back to before Iconia was destroyed, with the aim of ensuring no Iconians escape. However the Alliance ends up aiding the Iconians and securing their World Heart.
The battle is finally ended after the World Heart is returned to L'Miren. Although T'Ket's bloodlust is not yet satisfied and she disappears, the Iconians then officially end the war on the condition that the other powers of the Milky Way leave the Iconians in peace, who now plan to re-colonize Iconia.
A large-scale invasion of the prime universe in the Badlands led by Mirror Admiral Leeta begins. The Terran Empire, having defeated the Iconians in their dimension, establishes a foothold in the Badlands.
Meanwhile the Alliance makes official first contact with the Lukari when investigating the mysterious dimming of the Lukari System's star. There they come into contact with Kal Dano who uses the Tox Uthat to help the Lukari, but it is subsequently stolen by the Tholians and used against the Na'kuhl. The Na'kuhl become xenophobic and resistant to outside help as their people face the threat of extinction.
The new temporal technology available to the Alliance at the end of the war raises new questions on how it should be used. It also brings the Alliance into the Temporal Cold War where they aid temporal agents from the future in combating the Temporal Liberation Front. The TLF is led by Noye, one of the engineers who build the Annorax and lost his Tuterian wife during the Alliance's first temporal incursion. The Tuterian themselves, hiding in subspace, are joined by the Terrans and Na'kuhl in fighting against the Temporal Accords.
A New Dawn
- Federation starbase Deep Space K-13 is discovered in the 20 Draconis System, having been displaced from its original time and place in the Deneva System of the 23rd Century. The surviving Starfleet crew as well as a contingent of Klingon personnel are found in cryogenic stasis onboard the station.
- After years of secrecy the Tzenkethi Coalition begins testing a series of protomatter weapons in the Alpha Quadrant, prompting a response from the major powers of the Alpha and Beta Quadrants to determine their motives. At the same time, the Lukari begin to develop long-range warp travel and begin forays into interstellar exploration, aided by the Federation, Klingon Empire, and Romulan Republic.
- Long thought to be dead, Martok is freed from captivity in the Briar Patch. He returns to lead his house as a General, helping in the Alliance war effort against the Tzenkethi forces.
- The Nexus returns to the Alpha Quadrant, returning the alien entity known was Khaj'Buur as well as the long lost crew of the U.S.S. Forrestal.
- An expedition to the Gon'Cra Nebula results in the discovery of the Kentari civilization, the very same who had exiled the Lukari years prior, had relocated to New Kentar. Reunification efforts are expedited by the Alliance, who assist the two powers in creating a joint Lukari-Kentari colony in the Dranuur System.
- The Tzenkethi Crusade's brutality increases - now employing the usage of devastating protomatter torpedoes - and their targets are revealed to be the Hur'q, shortly after the Tzenkethi attempt to attack the joint Alliance-colony on Dranuur as well as the high profile target of Bajor. The Hur'q awaken during the attack and then assault Alliance and Tzenkethi forces over Bajor, before they are beaten back by Alliance and Dominion forces (the latter led by Odo).
- Odo convenes a summit at Deep Space Nine shortly after the aformentioned Hur'q attack, where he outlines that fighting the Hur'q in the Gamma Quadrant has stretched Dominion forces to their breaking point (Odo states that the Dominion has 'one fleet left'). While most of the Alpha and Beta quadrant powers agree that the threat posed by the Hur'q is too great to ignore, the Klingon Empire refuses to commit its forces to fighting them. The summit is interrupted when Hur'q forces attack Deep Space Nine again.
- The Dominion provides the Alliance with a cure for the microbes on the prison moon in the Olt System, thus frreing the prisoners. Former Bajoran Kai Opaka Sulan is among those freed, and she returns to Bajor. Kai Kira steps down as a result of Opaka's return and has her Starfleet commission reactivated.
- A combined Alliance-Dominion expedition to the outer reaches of Dominion territory discovers that Karemma is under blockade by another Dominion fleet, this one led by the Female Changeling. Further investigation reveals that a Hur'q Signalling Device has been placed on Karemma, and Garak reveals that another device was found on Bajor. Odo confesses to having the Hur'q lure placed on Bajor (thus explaining the attacks by both the Hur'q AND the Tzenkethi), but insists that Bajor was never in any real danger, and that information is being kept from him by other members of the Great Link.
- The Alliance and the Dominion defend Empersa from the Hur'q with additional aid from Klingon forces led by General Martok. Dukan'Rex sacrifices himself to cure the Hur'q and the Dominion is incorporated into the Alliance, removing their addiciton to Ketrecel as a condition.
- Gaul (Vaadwaur Supremacy leader)
- Kahless the Unforgettable's clone (Killed by T'Ket)
- Taris (uncertain, pushed off a precipice)
- Ambassador Woldan and most other members of the Klingon High Council (killed by M'Tara)
- Preservers (destroyed by Herald bombardment)
- Torg (Killed by Martok)
- Female Changeling (stabbed through the back by a Hur'q Mutant)
- Weyoun 10 (killed by Dukan'Rex)
- Dukan'Rex (self-sacrifice)
- With the remaster of the Delta Recruitment, the timeline has changed slightly where the first in-game confirmation of advancement to 2410 for all players is at the end of the recap-video introducing the mission “Surface Tension”, whereas “Butterfly” replaces “Cold Storage” in having the the on-screen date as "June, 2410. One year from now..." provided to Delta Recruits.
- Previously, the first in-game confirmation that the timeline has advanced to 2410 is provided in the Delta Recruit version of “Cold Storage”. As the on-screen date is given as "June, 2410," it is possible that one or more of the preceding missions also take place in 2410; however, this cannot be confirmed. For players who are not Delta Recruits, the first in-game confirmation that the timeline has advanced to 2410 is provided at the end of the recap-video introducing the mission “Surface Tension”.
- The first indication that 2410 has ended is in “The Measure of Morality (Part 1)” but it is unclear when in the year. IN the absence of frequent dating, some of the events listed above may occur in 2411.
- Official artwork on the STO website indicated that Starfleet introduces the "Odyssey" uniform as the new standard duty uniform for Starfleet officers in 2410, replacing the "Sierra" (though Subsection 2, Paragraph 1 of the Starfleet Uniform Code remains in effect; Starship captains continue to have discretion as to their personal uniform and the uniforms of their bridge crew). However, this uniform change was incorporated retroactively into the game, making all Starfleet personnel wearing the new design at any time, even in missions taking place in 2409, thereby creating some in-game ambiguity with respect to the exact time of the uniform change.