Da'an arrived approximately six years ago with the other Taelons, and quickly endeared himself to the American public. Three years after his arrival, he visited a Midwestern American town and was involved in a complex shootout that resulted in the apparent death of billionaire Jonathan Doors. The swift action of police officer William Boone sparked Da'an's interest in Boone, and Da'an was evidently responsible for the death of Boone's wife.
Da'an arranged for the limb regrowth of Julie Payton's hands, and was astonished when she regarded him as a messenger from God. Later, an attempt was made on Da'an's life by the murderer James Pike, who sought to kill him for the benefit of humanity.
Da'an was deposed from his position when Jonathan Doors was found to be alive and leading the Liberation. Boone assisted him in fixing his image before the Synod and regaining his position. These actions furthered his growing trust of Boone, whose unseen lack of a motivational imperative made him radically different from Sandoval.
Da'an was kidnapped by a group of renegade soldiers during a planetarium exhibit, who sought to find their abducted comrades. Da'an refused to reveal the location of the soldiers, saying that the Commonality did not wish it. The soldiers interrogated him, most notably Lucas Johnson, a man who had been altered physically by the Taelons. Soon after his capture, Da'an was compelled by the Commonality to end his life, slowly dissipating his energy. Boone managed to talk him into coming back as Sandoval came to the rescue. Respecting the near-fatally wounded Johnson, Da'an arranged for him to be hospitalized.
Da'an was helpful in containing the probe that attacked the Resistance, killing two people in the process. When Sandoval's CVI broke down, he ordered Boone to contain his fellow implant at all costs, fearing what Sandoval might reveal to the world in his overemotional state.
He opposed the project involving the devolution of a Taelon using human DNA, and attempted to help now-psychotic Taelon scientist Rho-ha. His advice helped William Boone sway a judge from using the death penalty on Rho-ha.
A Resistance computer virus caused a devastating shuttle crash, in which Da'an was not injured but Lili Marquette was. Da'an protected the wounded pilot from an explosion, carried her to safety, and treated her wounds as best he could. When the Resistance arrived, he stood up to the leader. After their rescue, Da'an "shared" his essence with Lili.
Da'an opposed another of Zo'or's projects, which involved bizarre implantations on portal passengers. When the Resistance scientist Sahjit Jinnah was captured, Da'an let him escape for the purpose of discrediting Zo'or before the Synod. When Earth was infected with a virus deadly to both humans and Taelons, Da'an saved Boone's life and produced an antidote for the Taelons.
He was upset when Zo'or killed Boone, but the immediate threat of a Jaridian replicant forced him to concentrate on the present. After Liam Kincaid saved his life at Boone's funeral, Da'an enlisted him as a new protector, sensing that Liam was not only human.
Da'an was accidently severed from the Commonality by Augur, and devolved into a barely-conscious Atavus, feeding on the life-force of humans. Liam was able to reconnect him, but Da'an was extremely traumatized by the event.
Da'an was targeted by a vengeance-seeking scientist who had developed a teleportation device, after putting himself at risk for the chance of bringing the murderer out into the open.
He isolated himself in a simulation of the Taelon homeworld, for a ritual known as the ka'arpaaj, in order to examine himself. Da'an was disturbed during this ritual by Zo'or, who revealed that a Taelon defector named Bel'li had crashed on Earth. Da'an was afraid at this news, but did not leave. Later, Bel'li attacked Da'an and was foiled by Liam, but Liam's trust in his charge was lessened by Bel'li's last accusation: "Do not trust Da'an. He will betray you."
Soon after, Da'an was given a terrible choice by Lili: allow Liam to die or give her access to the datastream. He chose to allow her access, but later felt betrayed when she attempted to destroy the mothership.
Da'an began to show more leanings toward his own species, but still assisted Liam in spiriting the Skrill Queen away from Sandoval's grasp. Their trust was shattered when Da'an hired an amoralist to wring Liam's codes out of Augur, and used them to gain Zo'or's trust. Liam was enraged when he discovered the truth, saying that he would have died for Da'an. Even if some of the trust has been regained, their relationship is still stormy.
The past came back to haunt Da'an when a pair of hybrid twins he created and abandoned started killing humans to save children they had created. He eventually took a hybrid baby and the girl, Belle, under his wing. He also opposed the use of the Taelon dueling sport Pad'ar as a human spectator sport.
When Zo'or entered the Taelon reproductive cycle, Da'an attempted to direct his emotionally unstable child back to the mothership. After a member of the "Cloister" was killed, Da'an incriminated himself, and vowed that he could never allow Zo'or to be harmed.
Da'an welcomed Taelon War Minister T'than to Earth, and discovered that T'than wanted to depose Zo'or from his position. Prior to a duel with Zo'or, T'than offered to accept Da'an as an esteemed friend if he abandoned Zo'or. Da'an did not reply.
Da'an experienced guilt and regret during a catastrophic incident involving the "Fields." After a heated fight with Liam about the morality of using humans to harvest "cryss", Da'an announced that cryss was not being made on Earth any longer.
Da'an found himself in a terrible position when Zo'or was haunted by the ghost of a suicidal Taelon who had been exiled from the Commonality. He could not condone what Zo'or had induced the Taelon Ku'don to do, but he had to help Zo'or banish the ghost or risk being exiled himself. He managed to cast off Ku'don, but his fear for his child's safety remained.
Da'an was nearly killed by a brainwashed Volunteer named Andrea Mazar/Emma King, who had rebelled against her Taelon masters and escaped with one of Ma'el's relics. Da'an pretended to be ill, but Zo'or discovered that he had been pursuing the encoded research alone for the past few years. Da'an lost Zo'or's trust.
When the ill Lili Marquette returned to Earth, Da'an detected her presence, and was highly emotional about what had happened before. Sandoval kidnapped Da'an, and his energy was siphoned into Lili to save her half-Jaridian child. When he realized that two innocents would die if he did not, Da'an offered his life to his friend.
Only seconds after the birth of Lili's child, a girl named Ariel, Da'an was encased in a crystalline husk, apparently dead. A few days later, the husk evaporated, and Da'an revealed that he had gone into crystalline hibernation to to protect himself from Lili's Jaridian husband. He was touched by Liam's description of him as "the best friend I ever had" while his protector believed him dead, but Liam angrily retracted the statement upon hearing of Taelon experiments on human women.
Liam and Da'an's relationship strengthened when a discovery was made: that Da'an was addicted to kryss. Liam confronted the irritable Da'an, who collapsed after Liam threatened to tell Zo'or. Upon being released from a hospital, Da'an admitted that he had been experimenting, trying to extend his lifespan with large amounts of kryss. Unfortunately, the kryss had addictive properties as well as leaving a toxin in Da'an's system. Da'an agreed to use a newly-developed substitute; however, Sandoval shortly arrived with "real" kryss, and offered it to the addict. Da'an repeatedly told Sandoval to "take it away," but the agent did not. Evidently, at some point Da'an succumbed and began accepting the drug from Sandoval.
Da'an accompanied War Minister T'than to the stasis wing when the younger Taelon's core energy began to dwindle. Later, Liam revealed that T'than had been murdered — and Da'an discovered that it was his own child, Zo'or. Upon Zo'or's revelation that he too is dying, Da'an allowed him to drain a great deal of core energy from his own body.
When a Jaridian warfleet was detected en route to Earth, Da'an was obliged to leave the planet when the mothership was redirected on an escape route. He sadly bid farewell to Liam, after giving Liam a vital piece of information — the Jaridians hailed Earth shortly before the Taelon arrival, warning humanity not to ally themselves to the Taelons, but the transmission was blocked. Da'an also sent a message of peace to the Jaridians, but it was later determined that the fleet was a hologram.
Da'an reluctantly agreed to become the recipient of Richard Palmer's "love" and "fear," in an attempt to regain a passion for life and thus survival instinct. The strength of these emotions soon overwhelmed him and made him unstable.
However, even after the emotions had been reintegrated into Richard Palmer, Da'an retained an intense fondness for Renee. His fondness was displayed when she discovered that exposure to Taelon energy had made her infertile. He offered her a regeneration lattice that would restore her fertility. But Renee was still angered by actions taken against her brother, and refused his offer.
Da'an assisted Liam in finding Renee when she mysteriously vanished into a wall, and later told Liam of the Taelons' reason for coming to Earth. He was attacked shortly thereafter while he was in an energy shower, but the stabs from an energy blade merely shredded the front of his jumpsuit.
Da'an's life-force soon reached the critical point, and he left Earth for a prearranged meeting with a Jaridian. They intended to meld into one individual, an Atavus from millennia ago, but Balvak was closer to death and died after the fusion. The Jaridian gave his energy to Da'an — ensuring the "curse" of a long life.
Da'an contemplated suicide when a mass of dark matter struck the mothership, but Liam was able to dissuade him. Circling near the mothership in a shuttle, Da'an shared a great deal of energy with Renee Palmer, in the hopes that the computer would read her as himself.
