I have never seen better tank than Sejuani. From that time I bought her, I used her as a full-support tank. So, most times I earn only assists and less kills (2-3).

Because of her she can move fast and easily in the jungle and she can run away from the enemy turret if she has low HP.

Now I will show you, how to towerdive with this snow-mistress. :)

IMPORTANT!
I suggest this champion build for Summoner's Rift (5v5), and at least 2 premade players (you and your lane-mate). --> Oral communication is a must (Skype, TS, etc...).

Frost (passive): Reduces enemy minions, monsters and champions movement speed by 10% for 3 seconds. This is really useful, because Frost is always work if you attack enemies with normal attack or .






Arctic Assault: Sejuani dashes forward and deals magic damage on enemies. Is it a con, that the first enemy champion stops her, so decide carefully when and where to use this ability. Great pro, that automatically causes Frost (passive) on enemies.






Northern Winds: Sejuani summons a blizzard around her, dealing magic damage in her area. It also increase the damage dealt by 50% with on Frosted enemies with .






Permafrost: This is your most useful skill as a tank. deals magic damage on Frosted enemies, and in addition, reduces their movement speed for 3 seconds! (30/40/50/60/70%)






Glacial Prison: Let's see Sejuani's ulti... An ordinary ranged magic damage ability. It stuns the first enemy for 2 seconds, nearby enemies stunned for 1 second. Always save this ability for teamfights! And then, save it for enemy champions who you stun and you can strike their ulti ( Fiddlesticks, Maokai, Nunu & Willump, etc.).

Let's see, why is this mastery tree.

OFFENSE
Summoner's Wrath: Exhaust --> Reduces target's magic resist and armor by 10%

DEFENSE
Most of these are evident (tank masteries), I think. But there is some what people use rarely.
Siege Commander: Reduces the armor of nearby towers. You and your mates can destroy the turret more easily.
Mercenary: Gain 8/16/24 bonus gold on champion kills and assists. As I said, you can earn more assists than kills with this build, so it causes less money. This mastery helps you earn a bit more money.

UTILITY
Summoner's Insight: Flash --> Reduces cooldown by 15 seconds. Flash is a life-saver skill!
Expanded Mind: +4/8/12 mana per level. More mana = more chance to use your abilities.

Yes, I can image your face, when you saw those items. Let me explain it...









Mercury's Treads: Enemy team has AP champions, so you need these because of magic resist. If happens, that enemy team hasn't AP carry (that is a big LOL), you can buy other shoe. I suggest you Ninja Tabi.









Warmog's Armor: It gives you very-very much HP. And then, 30 health regeneration is really good. And look that passive! You need it for towerdiving! Without this item don't even try kill champions under their turret!









Rod of Ages: More MP, more HP, more magic damage. And then, upon leveling up this item restores 250 HP and 200 MP.









Shurelya's Reverie: +350 HP, +15 MP regen and reduces ability cooldowns by 15%. And then, if you and your team need to run away, Shurelya's Reverie unique active gives you and your nearby allies +40% movement speed (!!!) for 3 seconds. Don't forget, you are a support tank. Your team will be thankful.









Frozen Mallet: I suggest this item in "really end-game". It gives you 700 HP and 20 attack damage. It sounds useless, but listen this: UNIQUE passive --> Physical attacks reduce your target's movement speed by 40% for 2.5 seconds.

You will need really much HP for towerdiving. That's why you need Warmog's Armor so early. But I swear, you will be unstoppable, and enemy won't escape.

If you and your mate (I recommend a ranged AD, f.ex.: Vayne, Caitlyn) see that enemy is on low HP, you can reach him/her under his/her turret. You have to use your . Before, you should use for extra damage (I dont recommend it because of too much mana using), after the just use . At this time your DPS mate need to hit the enemy. If you run out of HP, just Flash back to the bush, and run away with until you don't reach your turret. Dont forget to ping him/her fallback... you don't want the death of your mate, dont you? :p
!IMPORTANT! --> Try to save at least 80-110 mana for fallback, if you need to run to the inner turret (other team toverdiving, jungler attacks you, etc...).

The MOST IMPORTANT!
You are a tank. So, it doesn't matter, if you die. Always try to save your DPS mates. Use or/and to slow and stun your enemies, and give chance to your DPS mates to run away.

Blue buff: In early game it is a must, because Sejuani has very low mana and insane cooldowns. Ask help from your jungler (if he/she doesn't use mana) or your DPS lane mate.
Red buff: Not a must. But if you can... just get it.

Late game
There's some tips for late- and end-game. Around 4000 maximum HP, you will be immortal. If the enemy team has overfed DPS-es, it is really risky to continue towerdiving. As you saw, I didn't use armor and magic resist items. If you think, you can sell your Doran's Shield (if you need more money, sell your Shurelya's Reverie), and buy:
- Guardian Angel : enemy team has strong AP and AD carries
- Spirit Visage : enemy team has strong AP carry
- Randuin's Omen : enemy team has strong AD carry
Ask your teammates what to do, if they feel so over-power themselves, you can continue your insane towerdiving.

***ORACLE'S ELIXIR***





If enemy team has stealth champions ( Akali, Evelynn, Twitch, etc.), you will need an Oracle's Elixir. With this item you can see invisible enemy champions, but be careful! This elixir has medium range (750 radius). You are a tank, so you have good chance to survive an incoming attack from an invisible enemy.

You can do the same build I show you above, I just recommend you some changes.

Beginning







Buy Boots of Speed and three Health Potions instead of Doran's Shield. Don't try to kill your enemies underturret alone, wait your jungler teammate.
Recommended jungler mate: Shaco --> "Why?" --> He can slow the enemy just like you, so you have more chance to kill one, or both enemies. Recommended tactic: Wait the enemies being close to each other, and use your on them. Use Exhaust on enemy 1, Shaco will use his skill , so both enemies are slowed down. If you do a good teamwork, you can kill both. If you kill one, this is good. BUT! You are Sejuani, the towerdiver tank! Use again on the enemy, tank the turret damage, and let Shaco to reach and kill him.
If you have an other jungler mate ( Nocturne, Shyvana, etc.), I can't recommend a good tactic like this... But use always your and then . Very useful skills!

If your jungler isn't so active, you have to only defend your turret. If your HP is low, and enemies try to kill you under turret, Exhaust that one, what your turret attacks. If you got your ulti ( ), try to use it on both enemies and stun them. You will survive, and enemies will die. After you can say them: "You have been trolled."
If you dont survive the attack (Ignite or other debuffs), it isn't a problem, but ask your jungler mate or mid lane mate for help, and defend the turret.

+ Move easily in jungle
+ Fast moving between lanes (perfect for ganking)
+ Escape easily ( )
+ Ideal support in teamfights (high HP, slowing and stunning enemies)
+ Her passive is Frost, reduces enemy's movement speed by 10%, very useful for you and your DPS mates





- Insane cooldowns ("Sejuani ulti CD 150/130/110 omg!!!" by a friend)
- Low damage as tank
- Alone she is useless with this build
- Easy to fail in early-game with her (1-6 level)
- Without teamwork, you can forget your victory

Recommended combo:

Northern Winds --> Arctic Assault --> Permafrost --> normal attack + DPS mate(s) hit the enemy


If enemies want to run away, use this combo:

Arctic Assault --> Permafrost --> Glacial Prison

Try to use before enemies reach ther turret, and your DPS mates can kill it without risk. If you don't have time to stop them, you have to tank their turret, and let your mates to slain the enemies.