The whispers start with his training. Before that, even. Probably his adoption. He can't remember a life without them. They think he can't hear them, but he can, can because they're the same whispers echoing around in his own head. "Not as good as Shen," they say. Not as calm, not as focused, not as talented. Maybe not good at all. A second class ninja, at best, and no amount of work will ever close that gap. It hurts, but he can't blame them because he knows. They only speak truth.
It's not that he hates Shen. Not at first anyways. Shen is quiet, patient, and intelligent, his foil, his compliment, and the two are fast friends. They spend most of their time together, enjoying the games children create so effortlessly. "As close as brothers," the whispers say, and he's not exactly sure what that means because what's it like having a brother? But if it's like having Shen then it must be a good thing, and he's happy with that. Then they make a new friend, a bright girl named Akali, and he's not sure if she's a brother either, but he likes her and she's fun so it's all ok.
But it can't last. Can't last because he can't keep up. Once their training begins, Shen and Akali rapidly outpace him, mastering their lessons at an astounding rate. "Prodigies," the whispers say. "Best in generations." And it's not that he struggles exactly, because he doesn't, he's beyond the average pupil but he's not a prodigy. He's just a Zed, and that's not good enough. Shen has his near psychic defensive skills, Akali has her inhuman speed and fluidity, and even in everything else they excel. The only thing he excels in is being third best. "Zed is good too," they whisper, but he hears the unspoken condemnation. But not that good.
As he grows, so does his resentment, his frustration. His relationship with Shen becomes more and more strained, until their meetings are marked by a tension like a tightly wound bowstring. And as their friendship fades, their rivalry grows, and he pushes himself to his limits in an effort to surpass his brother. But he never can, because Shen is a mountain of sheer cliffs: icy cold and impassible, and there is no more chance of surpassing him than of reaching the moon. He stretches and stretches, but it remains far out of reach, cold and distant. But it doesn't surprise him. After all, he's just a Zed, and hard work can't bridge the gap between their talents. But he doesn't quit, he can't quit, because if he quits then what does he have left? "Zed trains so hard," they whisper, but he knows what they mean. Failure.
Akali tries her best to bring them back together. She still considers them both her friends and he knows it hurts her to see their division. And he tries to please her because he still likes her, maybe even more than he did as a child, but he can't, because Shen is everything he's not. Quiet, patient, intelligent, and talented. His foil, his opposite, and how could they ever get along? She tries to convince him they're more alike than he thinks, and suddenly he's furious. Furious because he realizes that she doesn't understand either, she's a genius too, a prodigy, and how could she understand how painful and hopeless it is just being a Zed? She backs away from him, hurt, and when he snaps at her to leave him alone she obeys. He apologizes later, but the damage is done and they both know it.
The evening of the celebration of Shen's inheritance of the title of the Eye of Twilight, she finds him away from the festivities, angry and bitter. She's at a loss, because all she can see is the friend she once knew slipping away, and all she tries to do to help him only seems to worsen it. But she tries again because she can't just let him go, and when she sits next to him he doesn't push her away. She tries to tell him he's also talented and that he'll find his place, it will just take some more time, but her words miss their intended effect and he whirls on her, livid. He doesn't want pity, he doesn't want reassurance, he wants something that's his, something where he's not a second rate substitute, and his whole life has been nothing but waiting and waiting and waiting and waiting and he's still stuck, nothing's changed, so kindly come up with a different suggestion. This time, when she leaves, chased off by the acid in his voice, he lets her go without a glance.
He finds himself in an abandoned temple, surrounded by forbidden secrets. He's supposed to shun this place, to detest it with every fiber of his being, but all he can see is a key to his chains. He grabs it without hesitation.