Taken from a Korean Website
http://forum.gamer.com.tw/C.php?bsn=17532&snA=51886&tnum=9Sejuani's basic attacks apply Frost, reducing enemy Movement Speed by 10% for 3 seconds.
> ==============================================
> 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
> ==============================================
> 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
> ==============================================
> 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.
magic damage and are affected by Frost.
> cost 100/100/100 Mana
> cooldown 150/130/110
Champion Info:
tag:tank
range:125
move speed:315
armor base:17.5 (+3.5 per level)
mana base:220 (+40 per level)
mana regen:1.29 (+0.09 per level)
hp regen:1.45 (+0.17 per level)
magic resist:30 (+1.25 per level)
hp base:450 (+85 per level)
attack:54 (+3.5 per level)
Please keep in mind that things may change, however; she looks like a frost themed Amumu.