Taken

The Taken are former members of various species corrupted by an individual using the powers of the Darkness. Whatever species an individual Taken once was, it is transformed into a more ghostly silhouetted reflection of their former self bound to mindlessly obey the one who converted them.

Origins
During the war between the Hive and the Ecumene, Oryx sought out the Darkness for power that would grant him the advantage. To this end, he murdered his sisters in order to gain an audience with Akka, the Hive Worm God of Secrets. During this meeting, Oryx killed Akka, recorded its secrets onto his tablets of ruin and contacted the Darkness directly. Having received the power he needed, Oryx resurrected his sisters and began to build an army of Taken, converting the soldiers of his enemies into shadow-like creatures bound to obey him. For his creation and mastery of the Taken, Oryx declared himself the Taken King and unleashed them against all who opposed him, including the Ecumene, the Taishibethi and the Vex.

The Taken War
Upon learning that his son Crota had been killed by the Guardians, a faction of Humans, Awoken and Exos empowered by the Traveller to protect Earth after the collapse of Human civilisation, Oryx invaded Earth's solar system in retaliation. As his fleet arrived at Saturn, Oryx engaged the Awoken fleet and destroyed them entirely, leading to the presumed death of their Queen Mara Sov. Afterwards, Oryx began to attack the Cabal occupation force on Mars, Taking several Cabal to grow his army. A single Guardian arrived to investigate and successfully escaped as the Taken overwhelmed the Cabal base on Phobos, warning the rest of the Guardians of the Taken threat.

Over the course of the Taken War, Oryx converted numerous Cabal, Eliksni, Vex and even his fellow Hive into Taken. Eventually, the Guardians were able to infiltrate Oryx's ship and establish a beachhead. Despite complications arising from the Cabal launching their own attack against Oryx and the Guardians requiring the soul of an ascendant Hive to access the deeper interior sections of the ship (namely Crota's), Oryx was eventually defeated and the Taken left leaderless.

The Witch-Queen
During the Red War, the Taken resurfaced on Io, seemingly drawn to light of the Traveller the Cabal Red Legion had been harvesting. So great was their presence that the Cabal were driven off of Io entirely, leaving Io to be fought over between the Taken and Vex. In an attempt to replenish their numbers, the Taken launched an invasion of the Vex stronghold known as the Pyramidion, intended to convert the entire Vex species into Taken. This invasion failed however, as the Guardians learned of their plot and destroyed their means of entry into the Pyramidion, leaving the few who successfully entered trapped and at the mercy of the Vex.

The Taken also held a presence on Earth, primarily in and around the dark forest within the European Dead Zone. They eventually advanced from this territory, seizing control of a nearby water treatment facility and under the command of a Taken Cabal. Disturbed by the apparent intelligence and strategy of the seemingly mindless Taken, as well as the Taken Cabal commander's former allegiance to the Red Legion revealing that new Taken could be created by others besides Oryx (the Red Legion only entered Earth's solar system after Oryx's death), the Guardians' leaders were forced to conclude that the Taken had a new leader.

After a mass prison break of the Prison of Elders and the murder of Cayde-6, the Guardians discovered that the perpetrator, the Awoken Prince Uldren Sov had been manipulated by a Taken Anhamkara known as Riven. As discovered by the Guardians and the Awoken, Riven was among the many Taken that had infested the Dreaming City and had been acting on orders from Savathun. After learning that Mara Sov was still alive, the Guardians agreed to destroy Riven, only to inadvertently trap the Dreaming City in an interdimensional flux between the universe and the Ascendant Realm, causing the Taken blight to consume much of the city. After three weeks, the Guardians tracked down and slew the de facto ruler of the Dreaming City, Savathun's daughter Dûl Incaru. However, this was planned and prepared for by Riven before her death. The Dreaming City was trapped within a perpetual time loop between the deaths of Riven and Dûl Incaru, repeating the three weeks of growing Taken infestation endlessly.

During the Endless Night crisis, the Guardians sought the aid of the Eliksni House of Light in order to remove the apparent Vex simulation plaguing the Last City. Eventually, the House of Light's Kell, Mithrax discovered the architect of the Endless Night was Quria, a Vex Mind that had been taken by Oryx long before the Taken War. From this point, Guardians infiltrating the Vex network encountered Taken fighting alongside the Vex, indicating that Quria had subjugated the latter. The Guardians later fought and destroyed Quria, dispelling the Endless Night and freeing the Vex from Darkness control.

With the destruction of Quria, Savathun, the Witch Queen of the Hive and sister of Oryx, seemingly lost control of the Taken. Presently, they serve her sister Xivu Arath, alongside the Hive and the corrupted Eliksni known as Scorn. According to Mara Sov, the Taken now answer to their original master. Not Oryx, but the one who granted him the power of taking. The identity of this master remains unknown.

Biology
Physically, the Taken still maintain the shape of their original species and form. However, their bodies are entirely pitch-black, with a white glow present from their lower halves. Their faces are obscured by a white light seemingly functioning as a sort of eye and they are often seen twitching when not in combat. When killed, Taken do not leave behind a corpse, but rather simply evaporate into nothing on the instant of death. However, when killed by damage directed to the glowing light in their faces, the Taken instead seemingly implode into the space where they stood.

The Taken are paracausal entities that were from various races and factions but later enslaved by the Hive god Oryx who corrupted them with the power of the Darkness. These creatures are enslaved both mind and body to serve Oryx the Taken King, making them mindless thralls that serve the Hive god.

After the death of Oryx, the Taken were presumed to have been reduced to a mindless horde, lashing out on instinct with no means of replenishing their numbers or fulfilling whatever purposes they could potentially have been left. However, it has since become evident that Oryx's sister Savathun has assumed command of the Taken. Additionally, certain Taken individuals have demonstrated some level of independence. For example, the Taken Cabal known as Grask the consumed seemed to have assumed a leadership role among the Taken on Earth. Previously, a Taken Hive known as Malok attempted (and failed) to replace Oryx after the Taken King was defeated. Riven also seemingly maintained its personality after being Taken, and Savathun seemed dependant on Quria to control the Taken on her behalf, as they seem to now oppose her at the behest of Xivu Arath.

According to a Warlock researcher named Asher Mir, the Taken emit large quantities of neutrinos when entering through the space-time continuum. In his Gambit game, the Drifter has developed a portal comprised of these neutrinos, allowing Guardians to simulate the 'feeling' of being Taken. Interestingly, the transformation does not seem to be permanent, as several Taken Awoken have been subdued and restored to their original selves, although the presence of light and dark within the Awoken may be a factor in their recovery.

The exact process of Taking has yet to be examined in depth. The most of it Guardians have seen involved Cabal being dragged into a rift in the air or of Vex being enveloped by large blights of Taken energy. Reportedly, those who have been abducted to be made into Taken are transported to the Ascendant Realm, where they are offered their 'new shape' by the one who took them. It is unlikely they accept the transformation willingly, as indicated by the presence of Taken Vex, as the Vex are unable to properly simulate and understand paracausal forces such as the Darkness.

Source

 * Destiny: Taken King