Stormfrost

Name: Stormfrost (after her stormy grey fur and white patches, and her tendency to be a little cold-hearted at times)

Gender: She-cat

Age: 40 moons

Clan: WindClan

Rank: Deputy

Attack Power: 50,000

Appearance: She is pale grey with black stripes and a white muzzle, chest, underbelly, tail tip and left front paw. She has very yellowy green eyes and large ears because her father was a Siamese kittypet, although Stormfrost never lets her kittypet relations stand in her way. She has very thick fur like her mother, and a longer tail than most she-cats. She is a physically strong she-cat and she takes very long runs on the moors every day to keep strong legs and lots of stamina.

Personality: Mostly concealed, but the emotions she just can't keep to herself are anger, jealousy and love.

History: She was born into WindClan as Stormkit along with her brother Bluekit and her sister Runningkit. She had a normal kithood until just before she was made an apprentice, when Bluekit sneaked out of camp to try and bring down a mouse he had seen from the nursery. The 'mouse' he saw was a rat, and it was almost bigger than him and Bluekit was easily defeated. Her mother Larchberry found Bluekit's body the day after, and when she told Stormkit and Runningkit, Stormkit swore revenge on the rats. When the kits were apprenticed, Stormkit, now Stormpaw, worked hard on her fighting techniques. She also went to the gorge every day in secret to get used to the water in case she had to follow her opponent through water. When a rogue attacked her hunting patrol near the end of her apprenticeship, she gave it scratches and bites it would never forget. When her leader chose her warrior name, Stormfrost, everybody believed it was because of her white markings. But her personality had a part in her name, too. Her sister, Runningpaw, was named Runningheart for her caring personality, the complete opposite of her sister. Runningheart and Stormfrost were never very close, as their personalities were complete opposites, and their pelt colours were different too, because Runningheart was a white short-haired she-cat with cream points.

Origins: Mother: Thick-furred WindClan cat with dark green eyes and dark grey tabby fur
Father: Siamese kittypet with dark blue eyes like Runningheart
So part WindClan cat and part kittypet, but she never mentions her father. She considers herself to be more WindClan than anything else, and she doesn't really resemble her father much.

Sounds like Stormfrost is a good deputy

I think you should make a small section on her family. Then you can talk more about Runningheart, because it seems like there are a few things you want to say about her.
I'd also like to hear about how her father and mother met and how her relationship with her father is (if it still exists). You should elaborate "kittypet relations" to add some cool edginess like

I like the detail about how she worked hard to be a good swimmer and that she continues to train her legs for running. That was a nice touch.

Overall, it's a great start and I like the little quirks about Stormfrost ^-^