UPDATED LAST 30.05.2012
ADDED NEW: Few uppgrades here and there =) Enjoy!

Hi, and thanks to look upon this awsome Sejuani guide :)

Sejuani is a champ that is good regardless to what Item Order you build. Because she scale mostly of Defence. Her skill's will be more or less the same.
So here is an Perfect Allaround Tank Build I selected out for you.

Sejuani is very easy to learn. Pretty much straight forward and nothing fancy. She is a Very Good Jungler AND Ganks Very Easy whit her QE Combo.

MY MISSION WHIT SEJUANI
Tank whit alot of Defence, Large Health Pool (HP), Alot of Movement Speed (MS), Crowd Control (CC), AoE and Cooldown Reduction (CDR).
Here do you get a great build to just jump into team fights and control them all. You name it, she got it. This build got it all to be the perfect Tank.

ABOUT BUILDING SEJUANI OFF TANK OR OFFENSIVE
Some people say if you only build Sejuani Tank, they will ignore you in teamfights. Or add more Damage. Really? That is completely wrong.
They cant just ignore you, and if they do. You can harass all so much, that they can not get to the position's they want in a Team Fight to kill YOUR Carry's. Cause the Carry's of the Enemy Team will try to take out your Carry's. So Harass and CC those, save ulti to protect your own Carry's and your team will win. (Hard to explain, all encounters are different) Its allabout Crowd Control.

If you build offensive items early also, you will be a very bad tank. Cause late game is to late to begin building defence.

Your Armor and Magic Resist is enough whit this build. Defence Scales to about 60% of this, after that another +100 Armor will only add another 15%. So more is Overkill. Its made like this so you cant get +400 Armor and become Immortal ;)
And the big Health Pool provides alot of damage done by your AoE Skill Northern Winds.

PROS

• Easy to gank with
• Great AoE
• Great Tank
• Great Slows
• Great Ultimate Stuns
• Fun to play

CONS

• Not very high dmg output towards single target's
• Easy to get carried away whit your ganking and get behind in lvl's ;)

Frost (Passive) - Sejuani's basic attacks apply Frost, reducing enemy Movement Speed by 10% for 3 seconds.
ABOUT: A very nice passive. Your auto atk slow the enemy's, perfect for a Tank. And whit the "E" Combo when you are ganking, its a deadly combo.

Arctic Assault - Sejuani charges forward to deal magic damage and apply Frost to enemies. Sejuani stops upon colliding with an enemy champion.
Range: 700
Cost: 70 / 80 / 90 / 100 / 110 mana
Magic Damage: 60 / 90 / 130 / 170 / 210 (+0.4 per ability power)
ABOUT: Really good for ganking. You can just charge in from anywere whit "Q", follow up by using "E".

Northern Winds - Sejuani summons an arctic storm around her which deals magic damage to nearby enemies every second. Damage is increased against enemies affected by Frost or Permafrost.
Cost: 40 mana
Cooldown: 10 second
Magic Damage per Second: 12 / 18 / 24 / 30 / 36 (+0.1 per ability power) (+1 / 1.25 / 1.5 / 1.75 / 2% of her maximum health)
ABOUT: Great AoE for farming and damage in Team Fights.

Permafrost - Sejuani converts Frost on nearby enemies to Permafrost, dealing magic damage and increasing the Movement Speed reduction dramatically.
Cost: 55 mana
Cooldown: 11 seconds
Magic Damage: 60 / 110 / 160 / 210 / 260 (+0.5 per ability power)
New Movement Speed Reduction: 30 / 40 / 50 / 60 / 70 %
ABOUT: Really great slow effect, I mean REALLY great. They are going in slow motion at this time while screaming F*** sitting at home!

Glacial Prison (Ultimate) - Sejuani throws her weapon, stunning the first enemy champion hit. Nearby enemies are stunned for a shorter duration. All targets take magic damage and are affected by Frost.
Cost: 100 mana
Range: 1150
Cooldown: 150 / 130 / 110 seconds
Magic Damage: 150 / 250 / 350 (+0.8 per ability power)
ABOUT: Stun is always a great ability and become very handy. Makes jungle ganking even more easy.

SKILL ORDER
W Q E. Max out E first, then W and take R 6/11/16.

ABOUT MY SPELLS

• Smite
• Smite is needed for fast jungle, and to eventually last hit Baron or Dragon. Also use it to steal either Blue Buff, Red Buff, Baron or Dragon.

• Flash
• Flash is very good to gank more easy or to run away. Great Initiator Spell and Escape Spell.

OTHER SPELL'S TO CONSIDER

• Ghost
• Can also be a good replacement, sence you already can go trough wall whit your Arctic Assault

• Heal
• Use this if you got the balls to take it. Also a good Option's.
  
  I am a Nudist, so hard to get rid off my Flash habits! You get it? damn im funny today.

ABOUT MY RUNE CHOICE

Greater Mark of Attack Speed
These are the best mark's if you want to speed up the jungle farm to the max.

Greater Seal of Armor
These are usually standard Seals you get on most champs, protect you against any psychial dmg.
Also the Seals you get for laning.

Greater Glyph of Scaling Magic Resist
Sejuani is a Tank, and most other stats except AP on Glyphs do not scale so good. MR is the best choice for her.

Greater Quintessence of Movement Speed
Yes, movement speed. It is ALL about the movement speed. These along the movement speed in defence tree AND utility tree. Oho yeah. Like a raging bully all over the map.

OTHER RUNE CHOICES
Greater Mark of Armor
Greater Mark of Magic Penetration
Greater Mark of Desolation
Greater Seal of Vitality
Greater Quintessence of Health
Greater Quintessence of Attack Speed
Greater Quintessence of Magic Penetration
Greater Quintessence of Desolation
Greater Quintessence of Armor
Greater Quintessence of Magic Resist

But those I recomended will be your best overall choice.

ABOUT MY MASTERIES
I choose 0/21/9obviously because she is a tank. And 9 in utility because this is an Jungle Guide.
I get Initiator in the Defence Tree AND Swiftness in the Utility Tree to Jungle faster and to Gank more easy.
Those along whit x3 movement quints? Yes, you can now catch up to anybody.

Cause if you can not catch anybody? Well, lets just say you are worth nothing more than a piggy scarecrow!

ABOUT MY ITEM CHOICE

• Cloth Armor + x5 Health Potion

• Boots
• Time to get some speed along the way. Gives you more mobility to farm jungle faster and to gank better.

• Philosopher's Stone
• This Item provides you whit health regeneration and mana regeneration. Helps you jungle smooth and to gank more easy. It also provides you whit extra +30 Gold pr minute.

• Heart of Gold
• Lets add more Health and ANOTHER extra +30 Gold pr minute. Wich obvious is a great thing.

• Phage
• Lets add some more slow and damage.

• Mercury's Treads
• About time to get even more mobility. All the enemy have +2 boots at this moment. And you get more tanky whit Tenacity Effect and Magic resist.

• Warden's Mail
• Lets start by getting abit more Tanky. This is an very good Item.

• Shurelya's Battlesong
• Now let us finish this Item. So we can get more Speed when needed and CDR.

• Randuin's Omen
• Lets finish this Item to get very hard to kill for AD Champs and for the Press To Use Effect. Also gives more space in Bag for new Items. If you want to build Frozen Heart instead of Warmog's Armor. And want it before Randuin's Omen? You can, but your Bag space will be limited. So that is why I build Randuin's Omen first.

• Negatron Cloak
• Lets get more Magic Resist in addition to your Mercury's Treads and Glyph Runes.

• Force of Nature
• Lets finish this Item to get really Tanky, more HP Reg and to get even more Movement Speed.

• Frozen Mallet More HP, Slow and Damage is really nice.

• Warmog's Armor Massivly Increases your Health Pool. It will also make your Skill Northern Winds Scale alot whit your max Health Pool. And you get additionally +40 Health Regeneration.

You can switch order of some items. Many of the games you will play, will be abit different. Its all situational, but this is my Core End Game Build I usually end up whit.

About Shurelya's Battlesong. What I usually do, I press it when teamfights are about to end. Either to chase remaining enemys that are trying to escape. Or if we need to escape ourself.
That is mostly what you do whit that item :) (or if you need to rush Drake or Baron)

OTHER ITEM'S TO CONSIDER
Other items to consider if you want a cheaper build OR the enemy team is "heavy" AP, AD or CC.

• Sunfire Aegis (+35 AoE Damage Pr Sec, +45 Armor and +430 HP, Can be switched for Warmog's Armor. You already got enough Armor, AoE Damage is helping just abit. And +430 HP VS +1270 HP and +40 HP Reg? And more HP = better Damage on your Northern Winds. I would myself go for Warmog's Armor if you consider one of those two items.
• Aegis of the Legion (I usually ask the support to make this item if it is needed)
• Banshee's Veil (vs AP)
• Frozen Heart (For even more Armor VS Heavy AD Team's. For 20% more CDR, for the Aura and it will increase your Mana Pool)
• Trinity Force (Can be swithced for Frozen Mallet)
• Hexdrinker (vs AP burst champs like Annie, LeBlanc, Brand, Ryze, Veigar etc)
• Quicksilver Sash (vs CC champs like Veigar Stun Combo, Ahri Charm, Rammus Tant etc and it helps VS Exhaust Spell's)
• Thornmail (vs AD champs like Tryndamere, Xin Zhao and top of that, it will help VS ad carry's aswell)
• Boots of Swiftness (Maybe if the enemy is full of mobility champs like Singed, Vayne, Ahri, Ashe etc. VS Champs that are hard to catch)

WHAT ITEM TO GET FIRST?

• Just pay attention to what the enemy have, and what your team needs.

IF YOU WANT AP INCLUDED
Rylai's Crystal Scepter and Abyssal Mask is an combo that makes out some dmg output. But if you are tank, I would not recomend that.

JUNGLE ROUTE

• Wolves (get help whit some dmg)
• Blue Buff (get pull) (gank top/bot if Enemy is low or pushing the Lane)
• Wraiths (gank mid if Enemy is low or pushing the Lane)
• Red Buff
• Golems (gank bot if Enemy is low or pushing the Lane)
• Wraiths (gank mid if Enemy is low or pushing the Lane)
• Always see arond if any Enemy push a lane. Go Gank.
  

FEW TIPS

• You can also start whit E, and not W.
  Get good pull at Blue. You get lvl 2. Get Q. And gank top easy right away . (or bot if map is vice versa, and if bot is warded. Then you can gank mid)

• Gank whenever you can. Pay attention to the Minimap. Charge in whit Q, followup by E.
  Wich result's into 3 things:
  1. They either use flash (worth it)
  2. End up dead (totally worth it)
  3. They get very low (also totally worth it)
  Wich again result's into 3 things:
  1. It will let your team mate to farm more easy.
  2. Zone out the enemy. So he/she can not last hit OR get lvl.
  3. Or get advantage in lvl's if he/she recalls for heal.

• If your Arctic Assault is on Cooldown. Then remember when jungle wolves, golems or wraiths. That you autoatk 2-3 targets before pressing E Permafrost. Then you get the most out of your damage, you want more target's to have Frost Passive on them. Otherwise Arctic Assault into/trough minions or jungle creeps, it automatic gives them all Frost passive.

• Remember to buy wards for your team. And I usually always get an Oracle's Elixir also, to prevent enemy to have map control for ganking and get to kill dragon.

Yes, Sejuani can also Lane. Start whit Philosopher's Stone, then maybe Boots and maybe Heart of Gold. Sometimes you have to skip to get another item. After that, build the items provided or from the Other Items To Consider Section accordingly to who you play against.

A BIG TIP
Whenever your own minions get low hp, harass the enemy player.
That will make them loose concentration whenever they want to last hit.
Gold win games.

WHEN TO INITATE TEAMFIGHTS

Its very important for you as the Initiator to Initiate at the right angle's, position's and at the right time.

Examples

• Do not chase an enemy into the Brushes mid/late game when you have no idea were the Enemy Team are (it may be a trap). If you have no qlue and no vision, be carefull.

• When a Team Fight starts, do not forget to protect you team mates. DO NOT get tunnel vision and chase a running target and leave your Team VS Enemy Team alone. Forget the 1 Player that are running and concentrate on winning the Team fight.

• Position yourself. Arctic Assault and Glacial Prison can be blocked by other Tanks, Off Tanks or Bruiser's. Position yourself to hit the Carry's and the Squishy Champs.

MY LAST WORDS
Sejuani is really worth buying. And whit this build, everything is working perfectly.
My damage output against single target is not among the best end game, but ok. But they can not kill me either. (and besides, your not the carry either. Its not your job to do the killing. AoE damage output is good, just autoatk 2-3 champs and Permafrost slow them all to hell. Or Arctic Assault into the enemy team and Permafrost. That also automatically apply Frost to the target's. And whit the Aura's and Press To Use item's. Yes, they are so handicapped. And top of that whit your Ultimate Glacial Prison? Your Team just rip them apart :) Love it!

Overall Sejuani is a Very Good Allaround Balanced Champ. Enjoy!

Best Regards
Rezpite (Tommy, Norway) <3