Hollyleaf

Warrior/self-imposed exile of ThunderClan, and a main protagonist of the Power of Three arc. She is sister to brothers Lionblaze and Jayfeather, both of whom are involved in a prophecy promising extraordinary powers and greatness that she is mysteriously excluded from.

Actually, Hollyleaf was originally supposed to be included in the prophecy ("There will be three, kin of your kin, who hold the power stars in their paws"), but because the authors did not come up with a power for her in advance, it ended up that she did not have one. So, rather than possessing an awesome ability like walking in other cats' dreams or invincibility in battle, Hollyleaf is primarily defined by her unhealthy obsession with the warrior code.

At first, Hollyleaf's weird attachment to the code does not seem to pose much of a problem, and comes across as more of a byproduct of her generally anxious and intellectual nature. As the books go on, though, and she struggles to deal with the weight of the prophecy (which ironically does not even apply to her) and the normal troubles that afflict the Clans when cats fight and steal prey and let their Clan be usurped by eclipse-prophesying weirdos, she becomes ruthless in her pursuit to protect the code, which is a bit out there in the context of this series.

This all culminates in her finding out that she herself is a living example of perhaps the worst possible contradiction of the warrior code: her true parentage is that of the Clan medicine cat, Leafpool, and a warrior of another Clan, Crowfeather. GASP! Because her Clanmate Ashfur was planning to reveal that her parents Squirrelflight and Brambleclaw were not really her parents to all the Clans, she decides the best option is to kill him to keep him quiet, but upon learning who her real parents are, she is driven off the deep end. In her mind, the code has been so broken that nothing really matters anymore, and with this absurdist attitude she simply takes Ashfur's inspiring idea and tells all the Clans herself. And then decides to kill her mother by forcing her to eat deathberries, which she ultimately decides against as Leafpool informs her it is a better punishment to just let her live. And then runs into the tunnels at the edge of her territory and "dies" trying to escape the Clans, seemingly crushed by soil. Rather dark for a children's series, no?

Hollyleaf doesn't return until five books later, and when she does we find out she has been living in the tunnels the entire time with this ancient dead cat named Fallen Leaves. Turns out she came back only to die again, as evil Ghost!Hawkfrost takes her out in book six. But it's okay, because before she goes she makes peace with her family and learns that life does not revolve around the warrior code (well, actually, I'm not sure she ever really learned that last part, as till the end she's still harping about it, but whatever).