Spottedleaf

Warriors: The UItimate Guide
"Spottedleaf was the medicine cat in ThunderClan when Rusty the kittypet, who would one day become Firestar, first arrived. She saw in him the same qualities that Bluestar did: courage, spirit, unwavering loyalty to doing the right thing. Spottedleaf also saw Rusty as a warm, sensitive cat who was not limited by his expectations of her role as medicine cat and who viewed her more than anything else as a friend. If things had been different--if Spottedleaf had been a few moons younger, an apprentice warrior rather than a medicine cat--their relationship would have become even closer.

Instead, Spottedleaf died before she and Fireheart could find a way to express how they felt about each other, which left her frustrated and lonely in StarClan, missing the friend she had left behind. She refused to let go of the connection she had shared with Fireheart, and walked in his dreams, guiding and supporting him in his early days of leading ThunderClan.

When Firestar left to rediscover SkyClan, Spottedleaf knew she had lost him to Sandstorm. In her heart, she understood that the young she-cat was a far better choice, able to walk side by side with Fireheart, bear his kits, and share responsibility for the Clan over the coming seasons. Spottedleaf grieved for missed chances, for a life that could never have been, but she still watched over Firestar and her former Clanmates as they moved to the lake and built new lives far from her forest home.

In the final confrontation with the Dark Forest, Spottedleaf gave her life in the stars to save Sandstorm, one last gift to her beloved Firestar."

Trivia

 * Some people believe that Spottedleaf was killed so "Firestar didn't have to choose between her and Sandstorm in StarClan
 * Spottedleaf's destiny was to save Sandstorm.
 * Taken form the book Warriors: The Ultimate Guide by Erin Hunter