Odo

Odo was one of one hundred unformed, or 'infant', Changelings sent out to explore the Milky Way Galaxy by the shapeshifting Founders of the Dominion, with a compulsion to return home later in life.

The Founders would originally claim that this was to gather knowledge of the rest of the galaxy by aborbing the experiences of the Hundred upon their return. It was later discovered the Hundred were, in fact, bait to lure the being known as the Progenitor, the entity that created the Great Link enmass and then left for parts unknown, to return. The Founders considered the Progenitor to be the one true God of the galaxy.

Odo was found in 2356 in his gelatounous state in the Denorios Belt, and brought to the Cardassian occupied planet of Bajor, where he was studied and later tutored by Dr. Mora Pol. Odo would later leave the lab that was the only home he knew, and relocate to the orbiting space station Terok Nor.

Terok Nor
Odo was recruited by Gul Skrain Dukat, the Cardassian Prefect of Bajor, to serve as the stations Chief of security in the year 2365. He would serve in the position past the Cardassian withdrawl and into the tenure of Starfleet, until the end of the Dominion War in 2375.

One of the first Bajoran deputies took on by Odo was a Bajoran man named Shul Torem. Shul would serve on the stations security force for over ten years. (novel DS9 Section 31: Abyss)

Odo was security chief when the station was quaranteened after being infected by a variation of the deadly Double Helix virus. (novel TNG Double Helix book two, Vectors)

Deep Space Nine
After the Cardassian withdrawl in 2369, the Bajoran Provisional Government requested relief efforts from the United Federation of Planets, and gave occupancy of the station to Starfleet, who rechristened it Deep Space Nine.

At First, Odo didn't think he was going to like the new stations commanding officer, Commander Benjamin Sisko, but after seeing how Sisko handled Odo's nemesis, the Ferengi bartender Quark, Odo warmed up to him. (episode novlization DS9 Emissary)

In 2371, Odo assisted Starfleet in preventing an assassination of Klingon Chancellor Gowron by former Starfleet officer and Maquis Thomas Riker, who was actually a pawn of the Romulan Sela. (novel TNG Imazdi II)

in 2375, Odo returned to the Great Link with the cure to a virus that was decimating the Changeling population in exchange for the Dominion's surrender in their war against the powers of the Alpha Quadrant. He left behind the woman he loved, Colonel Kira Nerys. (episode novelization DS9 What We Leave Behind)

The Dominion
Soon after arriving at the link, Odo confirmed that there was, indeed, genetic material on file for the cloned Vorta Weyoun despite previous claims. Odo had a new Weyoun cloned to act as his personal Vorta assistant.

Three months after rejoining the Great link, Odo assigned Taran'atar, a Jem'Hadar soldier that was not addicted to the drug Ketracel White, to travel to Deep Space Nine and act as an observer of the species of the Alpha Quadrant. Odo's hope was that the Jem'Hadar could eventually learn to be more than blood-thirsty soldiers. (novel DS9 Avatar book two)

Soon after dispatching Taran'atar to DS9, rumors reached the Great Link of a holy woman speaking of the Prophets and of healing. The rumors also said that this woman had had contact with a mysterious race known only as the Ascendants, a dangerous race that the Link knew very little about.

Believeing this woman to be the lost Bajoran Kai Opaka Sulan, Odo disguised himself as a Trelian woman named Wex and set out in search of her. Odo eventually found both Opaka, and Jake Sisko, who was on his own adventure in the Gamma Quadrant.

Opaka's knowledge of the continued existance of the Ascendants was important information for the Dominion, but Odo couldn't return to the link without first seeing Opaka and Jake back home to Bajor.

Upon arriving back at the station, Odo quickly found himself in the middle of the Parasite crisis. Reuniting with his love Kira, Odo assisted in the liberation of the Monastary at Ashalla, which was the stronghold of the alien parasites.

Odo stayed with Kira at DS9 for approximately a month, long enough to attend Bajors admitance into the United Federation of Planets. (novel DS9 Rising Son Unity)

The Progenator
Odo and fellow member of the Hundred, Laas, learned the truth as to why they were sent out into the galaxy as infants at the end of the year 2376, from a Changeling that Odo named Indurane, Bajoran for 'ancient'.

Indurane explained that the Great Link and all Changelings were created enmass by a god-like being known as the Progenator. There were no 'infant' Changelings, only Changelings that had not separated from the Link and begun to learn. This was why the Changelings had such restrictions on harming one another-- with each Changeling death, the species was brought that much closer to extinction.

The Hundred had been sent out to attract the attention of the Progenator and lure it back to link and replenish the species.

For a brief time, it appeared as if the Changelings had succeeded and lured the Progenator back when a nova appeared in the sky in the place where the Founders believed the Progenator would return to. But when a party of Changelings, including Odo, inspected the site, they found only the corpse of a gigantic Changeling, perhaps even the Progenator itself, killed by the radiation of the nova.

Several days later, the Great Link disolved in what appeared to be a mass suicide, as all of the Changeling that had hoping for the Progenators return seemingly gave into their grief.

This left only Odo, Laas, and perhaps a few other members of the Hundred running the entirety of the Dominion. As of this writing, the future of the Dominion is in question. (''novel DS9 WoDS9 volume three The Dominion: Olympus Descending