Kesivik was a dreg during the red war who had found a damaged ghost in a collapsed house thanks to its friends trying to transmat bits and pieces away from him. Seeing their struggle and seeing the injured ghost, Kesivik decided to help it. At first, the others scattered, and the injured ghost thought it was going to be hurt more or worse. But with nimble hands, Kesivik managed to get the ghost free of the debris and release it to its fellows. The ghosts quickly came, gathered around the injured one, and rushed away to a safer hiding place.
After being helped though, the ghosts began following him and leaving him useful gifts like berries and stuff to thank him for his help. This went on for a while until one day one of them actually comes to ask for his help because the injured ghost isn't doing well and in following them, they'd observed that Fallen worked really well with machines and that maybe they would be able to fix/heal whatever's wrong with him.
Kesivik tries but the little ghost has lost a lot of its inner light thanks to a slow leak in its core. So he now has to figure out how to fix and "refill" that core. He knows his crew's archon/servitor engineer has a Splicer's gauntlet (not unlike Misraaks') and steals it to try and help. The engineer finds out but decides to let things play out and actually helps Kesivik. Together, they head to the Shard of the Traveler to refocus light from it into the Ghost as they fix it and it gives Kesivik a glimpse and brief connection with the Traveler. Not enough to see anything important but enough to glimpse the Traveler's presence before the Ghost is healed.
With the ghost healed, the whole cloud of Ghosts (the ghosts 4 friends) celebrate and decide to stay with Kesivik as he is now their friend too.
Kesivik and the poor archon/engineer have a looot of explaining to do when they have to tell the crew about it.
However, after talking it out, the two decided it would be better for them and the ghosts if they kept the ghosts' & Kesivik's little friendship a secret, thus keeping both sides safe from the wrath of not-so-understanding Eliksni. In their place, however, the archon-engineer made the decision to take Kesivik on as an apprentice and decided to start teaching him to become a Splicer.
Kesivik was prodigious at it and soon began learning how to bend threads/traces of Light like he could Arc. Unfortunately, this led to further tampering with Light and it wasn't long before he tried to gather it and wield it like a Guardian could. This led to his downfall.
In attempting to gather and manipulate Light the same way he could manipulate Arc/Energy and small aspects of the Vex network, Kesivik strained the gauntlet and gathered too much power into one place, leading to a small explosion that both burned and blinded him.
Eyes that used to be bright ether blue now shine pearly white in complete blindness.
But the event was not without side effects. Since being blinded by the Light, Kesivik has been forced to use and hone his other senses - senses augmented by exposure to the Light he had gathered, allowing him to "see" through the Light - or at least see via auras caused by types of Light.
This skill of "Seeing through the Light" is not strong but it is bolstered when the Cloud of Ghosts (Quarry - the one he helped, Crystal, Iris, Barred, and Reeves.) came to assist. At that time, they decided to be Kesivik's blind-seeing-eye ghosts, helping him and showing his crew they were sincere and serious in their commitment to helping their friend.
As a member of House Dusk, he isn't exactly in the safest of places to be, but his crew (led by his aunt) keeps him either on their ship or in a safe cove-turned-bunker out in the dry sea in the Cosmodrome.
His aunt, (his last living relative), is still trying to find a way to make a life for herself, her crew, and her nephew without him being culled by their ruling baron who will not tolerate weakness or anyone considered a "drain or resources". It has been a difficult call on whether to keep him hidden away or to see if Misraak's "House of Light" will take him.
She and her crew can't just up and leave, but she hopes that he will be safe in the hands of the newly risen Light Kell.