BIOGRAPHY
Aikku Jokinen was a Finnish woman living in Norway when the Origin Bombs struck Earth. Ex Nihilo of the Garden had intended to redirect the evolution of the planet as a sentient, global organism using seven biological payloads fired at Earth from his base on Mars. One of the seven Origin Bombs crashed in the isolated forests of Holjanmyra, Norway where Aikku was backpacking. Aikku was drawn into the "pod" representing the self-defense System for the new sentient Earth, similar to the Starbrand created by Ex Nihilo's Builders in a later evolutionary System. This Pod system assimilated Aikku, trying to form a symbiotic whole with her as its chosen "user." Both Pod and Aikku retreated inside the larger Origin Bomb chrysalis as they evolved. Pod's Origin Bomb was unaccounted for by the Avengers and S.H.I.E.L.D. during their confrontation with Ex Nihilo, leaving A.I.M. free to harvest Pod for their own research purposes. [Avengers (5th series) #4, 38]
Pod and Aikku remained dormant on the A.I.M. Island of Barbuda as their organic and bio-mechanical systems integrated with each other. Meanwhile, the System of Origin Bombs came 
into conflict with the System initiated by the White Event and its avatars, Starbrand and Nightmask. Starbrand accidentally destroyed the self-awareness site in Croatia, and the self-repair site in Chhatarpur, India was unable to compensate for this loss. The communication site in Perth sent out a signal to the Builders and other sites on the planet, trying to find a solution. This signal erupted roughly every eight minutes, causing worldwide power loss and resulted in catastrophes. The Avengers were occupied dealing with the signal in Perth and the giants of India that arrived to support it.
A.I.M. recognized the connection between their find and the other Origin Bomb sites, and one of the scientists had the idea of copying the Perth signal and replaying it on a loop directly at the self-defense pod. This caused Pod to awaken before it and Aikku were properly finished bonding with each other. Pod exploded out of A.I.M. Island and made its way to Perth at supersonic speeds, instinctively responding to the call. Still geared up from battling the previous Origin Bomb sites, the Avengers reacted with hostility when Pod arrived. Aikku was confused and scared inside of Pod, unable to fully process what had happened to her yet. Reacting to both internal and external strife, Pod attacked the Avengers in a misguided attempt to protect its user. After the entire Avengers roster was laid out, Superia and A.I.M. approached Pod to recollect her. They used their dimension-spanning Auger to cast Pod into the space between dimensions lost to the Incursions, leaving her in "safe-keeping" until A.I.M. thought of a use for her. [Avengers (5th series) #14-17]
While lost in no-space, Pod and Aikku had the opportunity to communicate without distraction. Aikku also learned how to open the Pod armor. Although she could not completely disengage from her symbiosis with Pod, this allowed her the chance to observe her new form from the outside, leading to greater understanding. By the time Sunspot of the Avengers claimed A.I.M. in a hostile takeover and returned Pod to Earth with the Auger, Aikku was much more centered and accepting of her new situation. She began serving as Sunspot's bodyguard as DaCosta assembled his own Avengers during the Incursion crisis.
When the Galactic Council recognized Earth as the lynchpin of the multiversal crisis, they planned to destroy it. Aikku helped the new parents Cannonball and Smasher by enveloping their boy Josiah into her Pod shell, prepared to hide the child in no-space with her as Earth came under attack. And, as the final Incursion between Earth-616 and Earth-1610 came underway, Pod stood alongside the most powerful heroes of her Earth, such as Hulk, She-Hulk and Colossus. [Time Runs Out, Secret Wars #1]
The multiverse survived, after a fashion, and Pod continued to serve as bodyguard to Sunspot as he reformed A.I.M. into the new Avengers and Avengers Idea Mechanics global rescue operation. 
Aikku tried to rebuild the life she was pulled from by the Origin Bomb, but faced heartbreak instead. Her girlfriend Darja Vollun was unable to accept Aikku's new form as Pod, and their relationship did not survive this change in circumstances. Aikku's depression began to deeply affect her emotional state but, because she constantly rested inside the all-encompassing and inscrutable Pod armor, no one noticed. [New Avengers (4th series) #1-3]
No one but Toni Ho. The daughter of Ho Yinsen and a triple doctorate before age 20, Toni was chief of A.I.M.'s engineering division. Her attention to detail during the maintenance and 
assessment of the Pod armor led her to recognize that Aikku was not okay. She reached out to Aikku and the two of them bonded as Toni tried to literally and figuratively help Aikku come out of her shell. When A.I.M. utilized the Avengers Five robot based on the old Quintronic Man, Aikku and Toni also touched minds, bringing them a deeper understanding of each other. [New Avengers (4th series) #3, 10]
During their talks, Aikku and Pod finally revealed the true nature of their bond with one another to Toni. The Pod sentience was a unique intelligence born of the symbiotic bond between the armor and the user. Aikku was not trapped in the armor -- she was fully capable of leaving the Pod suit anytime she wished, but doing so would end their connection and "reboot" the Pod consciousness, effectively killing the A.I. that Aikku had come to regard as a sister.
Tragically, the decision was soon taken out of their hands as the Maker and his New Revengers infiltrated A.I.M.'s base of operations. The evil Reed Richards from another dimension had 
devised a weapon that caused terminal damage to Pod even with her reconstructive abilities. Toni fought to preserve Pod and Aikku's lives, but ultimately Pod sacrificed herself to save Aikku. Recasting what remained of its armor as a chrysalis of sorts, Pod expelled Aikku from their bond with a fully-functional undersuit of armor, leaving the larger and damaged Pod armor behind. Pod's consciousness faded away and flatlined, despite Aikku's tearful good-byes. [New Avengers (4th series) #12-17]
In her new identity as Enigma, Aikku discovered her undersuit retained an array of new and unique capabilities for her to master. With Toni adopting a role on the field team using her Rescue 
armor, the two women were now working side-by-side even more than before. As they took down the renegade A.I.M. terrorist cells together for Sunspot, Aikku expressed herself to Toni despite her broken English. She was eternally grateful to Toni for staying by her side during her depression and working to save Pod. With her new armor completely removable, Aikku was ready to begin interacting with people again, and with Toni most of all. [New Avengers (4th series) #18]
As part of a new deal with S.H.I.E.L.D., Dacosta converted Avengers Idea Mechanics into American Intelligence Mechanics, a sub-division of the larger defense agency. Enigma and Iron Patriot became field agents for the U.S. Avengers on behalf of A.I.M. As they worked together, 
however, Aikku began to notice behavior from Toni that worried her. Aikku and Toni had fallen in love over how focused and intense Toni was at trying to reach Aikku inside of Pod. Aikku now noticed that Toni's dedication to projects was so absolute that she neglected self-care, such as eating and sleeping. Aikku was also concerned about Toni's contradictory rejection of weapon engineering while also building more and more aggressive versions of her Iron Patriot armors. Still, she tried to support her girlfriend as best she could, while providing advice where she thought it could help. [U.S. Avengers #1-5]
When America was taken off-guard by the rise of Hydra, the U.S. Avengers were no exception. As their own troops turned against them from within S.H.I.E.L.D. and A.I.M., Toni remotely triggered an advanced phasing trick in Enigma's armor, launching her and Squirrel Girl to safety by phasing them through the planet and all the way to Paris. Over the next several weeks, Aikku and Doreen worked alongside the Champions of Europe to prevent Hydra from spreading its tentacles beyond the borders of America. [U.S. Avengers #6-9]
After they reunited, Enigma found Toni was in a better place mentally. She had been incarcerated in a Hydra camp, but escaped through the use of brainpower instead of weapons, leading her to step down from the troubling Iron Patriot identity and concentrate on pure research instead. Although Aikku was initially worried that having NO projects was just as bad for Toni as before, she needn't have worried. Sunspot stepped down as Supreme Leader of A.I.M., and the rank-and-file voted Toni as his replacement. [U.S. Avengers #10]
During the conflict between the Grandmaster and Challenger on Earth, Enigma was one of many heroes kept in stasis for the majority of the game. She emerged as a player after Red Wolf claimed one of the pyramoids and was removed from the board. Avengers Auxiliary Headquarters came under attack by the Hulk as the Challenger guided him to retrieve the last of the pyramoids. Aikku shifted her armor to maximum density as a bulwark against the Hulk's advance, but it 
proved ineffective. The Hulk was strong enough to rip the ultra-dense armor right off of Aikku's body, seemingly destroying the Enigma armor for good.
In the aftermath of the struggle, the U.S. Avengers disassembled as most of their members were depowered or went their separate ways. Toni threw her energies into rehabilitating the benevolent forces of A.I.M. into her new R.E.S.C.U.E. organization, with Aikku by her side. Whether the Enigma armor can be repaired at this point is unknown, but Aikku and Toni are determined to make a better future, and to face that future as a loving couple. [Avengers (1st series) #675-690]