Sejuani, the Winter's Claw - Next Week's Champion!

A wild Tepig appears!

If you've noticed Phreak's new Champion Spotlight Release on Jax on the right-hand sidebar, you might have seen this interesting little bit in his description that he posted:

Welcome to the Jax Champion Spotlight, summoners! For those who aren’t quite familiar with Jax, he’s a melee fighter and an exceptional duelist, able to quickly close into melee against his enemies. For those who are long-time fans, Jax will be receiving a major update in the Sejuani patch, complete with new abilities, mechanics, particles, and animations. Whether you’d like to learn a new fighter or just get a sneak peek at the changes, take a look at the Jax Champion Spotlight!

 As for who Sejuani is, it's quite a mystery...or is it?

Click Here for Sejuani Patch Notes

EDIT: Thanks to Timjin for finding her real kit on that forum! I've reposted it below for convenience:

Passive: Sejuani's basic attacks apply Frost, reducing enemy Movement Speed by 10% for 3 seconds.
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Arctic Assault (Q)：
Sejuani charges forward, dealing 60/90/130/170/210 (+0.4) magic damage and applying Frost to enemies. Sejuani stops upon colliding with an enemy champion.
> cost 70/80/90/100/110 Mana
> cooldown 19/17/15/13/11
> range 700.0
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Northern Winds (W)：
Sejuani summons an arctic storm around her for 5/5/5/5/5 seconds, dealing 12/18/24/30/36 (+0.1) (+ [1/1.25/1.5/1.75/2% of maximum Health]) magic damage each second to nearby enemies.
> Damage is increased by 50/50/50/50/50% against enemies affected by Frost or Permafrost ( magic damage per second).
> cost 40/40/40/40/40 Mana
> cooldown 10/10/10/10/10
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Permafrost (E)：
Sejuani converts Frost on nearby enemies to Permafrost, dealing 60/110/160/210/260 (+0.5) magic damage and increasing the Movement Speed reduction to 30/40/50/60/70% for 3/3/3/3/3 seconds.
> cost 55/55/55/55/55 Mana
> cooldown 11/11/11/11/11
> ==============================================
Glacial Prison (R)：

Sejuani throws her weapon, stunning the first enemy champion hit for 2/2/2 seconds and all other nearby enemies for 1/1/1 second. All affected targets take 150/250/350 (+0.8) magic damage and are affected by Frost.
> cost 100/100/100 Mana
> cooldown 150/130/110

Back in February 26, 2011, there was this fan post on the EUW forums that turned out to be a fake:

Sejulani is a bruiser designed to tank and initiate, focusing on movement, timing and positioning. Her skill set is intended to help her and her allies close gaps, disrupt and interrupt during team fights and with good timing reflect spells back. Her resource is mana based and her abilities have a reasonably high cost, Sejulani's passive rewards her for staying in combat longer. Her concept revolves around her fighting prowess, famed, single handily slaying some of the most powerful creatures in Runeterra. 

Passive - Chilled to the bones
As Sejulani takes damage her body slowly turns to solid ice, increasing her defence by x%, upon death her entire body is encased in ice, causing her to shatter, immobilizing those around. 

Q - Black Ice
Sejulani freezes the ground in a line in front of her, increasing allies movement speed and slowing enemies who walk over it by X%. 

W - Mirror Shield
Sejulani encases her shield in a layer of enchanted ice, reflecting back any spell targeted at her for X seconds. Does not affect area effect spells. 

E - Winter's Claw
Sejulani coats her claw in solid ice, extending her melee range and dealing additional damage for 4 hits until the ice shatters.
Champions affected by Black Ice are immobilized for 1.5 seconds if struck. 

R - Avalanche
Sejulani slams both claw and shield into the ground, summoning a devastating avalanche that deals x damage and knocking those caught in it forward.

Accompanying Fan Art

It's doubtful that the hero released will be the same one, but it's interesting to note. As for who Sejuani REALLY is, according to League of Legend's Wikia:

The tribes were reigned by the three Princesses: Ashe, the Frost Archer; Lissandra, the Ice Dervish; and Sejuani, the Winter's Claw.

The third of the Freljord Princesses – Sejuani, the Winter's Claw – remained fiercely adamant in her opposition of the other two. Sejuani retreated to isolation with the elders of her tribe. This caused concern among the members of the other tribes, who believed she may be readying for war.

The arrival of the barbarians, some predicted, was due to an invitation from Ashe to Tryndamere in order to deter Princess Sejuani from taking any aggressive action.

Ashe later offered Sejuani, the Winter’s Claw, a seat on Freljord’s new Royal Advisory Council. Sejuani emerged from her reclusion to respond, stating that she would never accept Princess Ashe as her Queen, and that anyone who does so was contributing to the perversion of their culture.

To read the full text of the lore check it out here

Got more clues? Post them below!