Corrupted by dark energies early in her life, Eki came to accept her curse as a blessing, and harnessed the power of dark waters in the defense of the entire Universe.
((Things in bold are to do with the Cyclic Plane Storyline and aren't necessarily canon.))
Eki was a Ga-Matoran living on the island of Poliaz. She was best friends with Soleku, and together with her formed the band known as Cyclestone.
During an incident where the island's toa protector, Tolovan, was corrupted by Gorast, Eki was caught by a blast of shadow and became a Shadow Matoran.
Eki collapsed into a coma. When she awoke, she was in the Palace of Shadows on Korrothis. Korrothis was an island seen as holy by most beings in the Matoran Universe. It was located in the perpetual glow of Mata-Nui's heartlight, and was the home of the Elemental Council - eight (nine counting Mata-Nui) beings who were one with the elements and regulated the balance and "natural" order of the Matoran Universe.
Brought back to health by the Kra-Nui, Nivorn, Eki was given a choice to either have her inner light restored, or to learn how to use her newfound powers. She chose to train on Korrothis. She later learned that her friends Soleku, Gratigan, Gringat and Xalos had become the Toa Vanembar. She helped them from time to time.
Eki was exposed to a strange device in the Shadowcaverns while helping the Toa Vanembar deal with a conflict with the subterranean Ak-Matoran. The device loaded her with Toa Energy which slowly suffused her being and transformed her into a toa, despite her not being destined to become one.
Though nobody could say for sure whether or not she was destined, her unnatural transformation brought up a dilemma amongst the Elemental Council. The Ta-Nui, Delnok wished to have her destroyed as she was a perversion of the natural order. The Onu-Nui, Reglas and Ko-Nui, Azmyrus wished to dissect her and study her. Nivorn and Ia advocated her staying on at Korrothis to study her own powers.
After a long and agonising debate, and more than a little pleading for her life, it was decided that she should stay on Korrothis and study her own powers. She later learned that Nivorn had acted out out of love, and admiration of her. They grew close.
Formally training under the Ga-Nui, Tolus but in reality spending most of her time at the Palace of Shadows with Nivorn and Ia, Eki studied, trained and meditated to bring forth her elemental powers. Her "natural" Water abilities were tainted by Shadow, giving her both of these as well and some elemental Acid powers. Her Great Kanohi Rau gave her the ability to read ancient texts and gain a greater understanding of the Elemental Weave.
Eki and Soleku were reuinited after Lianyu brought her to Korrothis a few hundred years later.
Eki's great knowledge of the Weave and her powers made her an ideal candidate to act as a teacher for new toa who came to the island to learn to control their powers. Again, this was opposed, but Soleku was able to help convince Delnok to see reason. Eki proved to be one of the best teachers on the island. Tolus compared her to a long-dead friend of his, Matara.
After the Reformation, Eki was left with both her best friends dead and her lover murdered by Teridax. She stayed with Tolus a while, but after he passed away she left to go explore the Great Ocean by herself for decades.
After exploring the sunken ruins of The Codrex, she suddenly returned to Korrothis with news that there were other worlds the Great Beings had settled! On her insistence, the vaults under the village of Drachen's Hope were cleared of Azalgor Crystals (very dangerous) and an ancient robot known as The Decipherer was uncovered which had knowledge of a world called Atmos Magna. Eki was among the very first to volunteer for a spacefaring mission to this world, using Korrothis as an ark to transport them there.
I made Toa Eki in 2013, kinda randomly. She was always a character in my storyline, but until recently her role in it wasn't very well fleshed out. She's one of my favourite characters, partially because she's one of the few who truly understands the world around her, partially because she's in love with a makuta (though she's not the only one...) , and partially because she's at the heart of so much conflict that happens in the MU storyline and stays a good-hearted follower of the Hexarc throughout.
The Matoran form was made recently and right now is exclusive to TTV Messageboards. She was originally made in 2010 and wasn't so cool looking though:
As far as I'm aware, Eki 2 and 3 don't use any designs from other MOCers (the first's foot design is by Lachlan "Xinlo" Tocher). LDD instructions for her hand design (used on another MOC) can be found here!.
Eki got featured in the Gallitor Report, too... I also voiced Roy Kneepole in that same episode. Please forgive the terrible voice acting :v