As of Picard season three, episode three, we finally know who the true villains of the season are. And they are perhaps the biggest threat the Federation ever faced. No, not the Borg. Not even the Klingons. We’re talking about the Dominion, a despotic intergalactic empire that waged war against the Alpha Quadrant for a solid three seasons of Star Trek: Deep Space Nine. In fact, they were such a threat that the Federation allied with both the Klingons and their longtime enemies the Romulan Star Empire to save themselves.

But just who, or what, is the Dominion? And who are their mysterious shape-shifting Founders, now causing so much trouble for Admiral Jean-Luc Picard (Patrick Stewart) and his friends? The answer goes back to the very first episode of Star Trek: Deep Space Nine, over 30 years ago. And one of the Star Trek franchise’s most beloved characters.

Odo, Deep Space Nine‘s Friendly Changeling

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The very first member of the Founder’s species we met was Odo, the shapeshifting chief of security aboard starbase Deep Space Nine. He was portrayed by René Auberjonois, and appeared in “Emissary,” Deep Space Nine’s first episode in 1993. Odo’s natural state was liquid, but he could hold a humanoid form for several hours a day. They found him as an infant blob near the Bajoran wormhole. This implied his species came from the distant Gamma Quadrant, where the wormhole connected to.

A Bajoran scientist named Dr. Mora gave the infant the name Odo, and he mimicked his humanoid shape as a tribute to him. Odo did not know where he came from. Or even what species he was. But he knew he liked order, and chose a life in policing. He became Chief of Security on Deep Space Nine. First, under the Cardassians, and later, under the Bajorans. However, he never stopped wondering about his origins. This longing for a people he never knew factored heavily into Odo’s character in the first few seasons of DS9.

The Dominion, the Anti-Federation

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At the end of season two of DS9, we learned of a major power in the Gamma Quadrant–the Dominion. This empire enslaved many planets. Their hierarchy consisted of a group of genetically engineered lizard-like clone soldiers, known as the Jem’Hadar. Their administrators, a humanoid race called the Vorta, gave the reptilian Jem’Hadar their orders. As well as the drugs they needed to survive. The Vorta maintained their orders came from the Dominion’s mysterious “Founders,” who they worshipped as gods. But no one had ever seen these Founders, and most species in the Gamma Quadrant considered them a myth.

The Dominion Founders Revealed

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By the time of the end of DS9 season three, Odo made a shocking discovery in the Gamma Quadrant. On a rogue planet in the Omarian Nebula, Odo discovered his people at long last. They were a group of Changelings just like himself. They existed together in what they called “The Great Link,” a large liquid mass where they all joined as one consciousness. Unlike the hive mind of the Borg, they could retain their individuality and leave the Great Link if they wished. Odo was an infant the Changelings let loose into the cosmos with 99 others. Upon maturation, it was meant for them to explore the galaxy and come back to the Link with what they had learned.

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At first, Odo was overjoyed to discover his people. But then he learned the terrible truth. The Changelings were themselves the mysterious Founders of the Dominion. After persecution by what they called “solid” species, they exerted control over the galaxy so no solid beings could harm them ever again. They genetically enhanced the Vorta, one of the few humanoid species to show them kindness, and created the Jem’Hadar as their foot soldiers. For 2,000 years they inflicted terror in the Gamma Quadrant, forcing worlds into their Dominion. Odo, disgusted with what he learned, left the Great Link and returned to Federation space.

The Dominion War Unites Former Enemies Against a Common Foe

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But that was just the start. The Dominion decided to conquer the Alpha Quadrant, and had their Changeling agents infiltrate the ranks of Starfleet, the Klingon Empire, and others. They infiltrated Federation starships and sabotaged them, and manipulated the powers of the Alpha Quadrant against each other, causing a brief war between the Klingons and the Federation after decades of peace. Eventually, the Dominion waged a full-scale war against the Federation. Starfleet had to unite with their enemies the Klingons and even the Romulans to save the galaxy. Meanwhile, the Dominion and the Cardassians, longtime Federation enemies, forged an alliance. This prolonged conflict they named The Dominion War, and covered seasons five to seven of DS9.

An Attempted Genocide Averted

The Dominion War ended due to the shady actions of the secret off-the-books Starfleet Intelligence agency called Section 31. Against Federation principals, they engineered a genetic virus they implanted into Odo, one meant to cause the genocide of the Founders when he bonded physically with any other Changeling from the Great Link. This action disgusted many in Starfleet, who were against the genocide of a race, even a hostile one.

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Starfleet doctors engineered a cure for Odo, one he could administer to the rest of the Great Link should he choose to rejoin them permanently. He chose to return, on the condition the Dominion end the war on the Federation and its allies, and leave the Alpha Quadrant in peace. With this action, the Dominion War ended, after the loss of millions of lives. They signed the Treaty of Bajor on station Deep Space Nine, in the year 2375.

Revenge of the Changelings

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When Picard season one began, it was close to 25 years since the end of the Dominion War. We’ve had little knowledge of the fallout of this great galactic conflict. But in Picard season three, Worf reveals that certain parts of the Great Link did not agree to the treaty with the Federation, and have broken off into a terrorist faction. Worf learned of this information from his contact within the link, someone he considered “a man of honor.” This was no doubt a reference to Odo himself.

So is Captain Vadic (Amanda Plummer) a Founder herself, or does she merely work for them? And what is her obsession with Jack Crusher? As we learned in Star Trek: Insurrection, the Enterprise-E under Picard’s command spent much of the Dominion War conducting peace negotiations and were not part of the fighting much. So a vendetta against Picard himself would be curious. But then, we really don’t know everything the Enterprise was up to during the Dominion War. While there is much still left to be revealed, one thing is certain — the Federation’s most lethal enemy is back, and they have not forgotten their humiliating defeat at the hands of the Federation.