PLEASE NOTE: Build is still in progress, I'm almost done though. :)

Nunu & Willump is a great AP Caster, either solo, with a lane partner, or even at mid. His abilities offer a great playstyle, allowing great sustainability with Consume, good support with Blood Boil, and great nuking with Ice Blast and Absolute Zero.

Although he's great as a caster, don't forget to look at his jungling capabilities, because with Consume, he makes one of the best junglers in the game.

Freljord is an unforgiving land covered in snow and ice. Travel, especially in the winter, can be very dangerous. The elements often claim even those who have spent their entire lives there. The boy known as Nunu is defined by such tragedy. One day when he was a young child, Nunu rode on his father's back as they returned from a trapping expedition in the mountains. An unexpected blizzard came upon them, forcing them to seek refuge in a cave. The tempest was the worst in countless years, and it lasted for days. Nunu's father left to find food, but he never returned.

The blizzard eventually cleared, and the young child lay dying on the mountainside. Fortunately for Nunu, this was the land of the yetis, who are powerful beasts with whom Nunu's father had secured and arrangement for safe passage. A young yeti boy named Willump found Nunu and brought him home. From then on Nunu was raised by the yetis, whose culture remains a mystery to most Runeterrans. The boy quickly discovered that the seemingly savage creatures were in fact deeply spiritual beings living in harmony with their environment. They are very territorial and unafraid of defending themselves if called upon to do so. The yetis have watched the rest of Valoran, and they can smell the change on the wind. When the League of Legends was formed, the yetis knew they needed a champion. Riding his brother Willump, Nunu became that champion. Those who follow the League know that the boy is mature beyond his years, but, while he appears human, his mind is that of his adoptive kin.

If this is him now, imagine what Nunu will be like when he grows up!

Pros:
*Amazing lane sustainability with Consume.
*Great when laning with a champion reliant on Attack Speed with Blood Boil.
*Great ganking with the slow of Ice Blast and his Blood Boil speed buff.
*1:1 Ability Power ratios on Consume and Ice Blast, with a crazy 2.5:1 ratio on Absolute Zero.
*Generally tanky, so he can survive a lot, especially if you use Consume correctly.


Cons:
* Absolute Zero is an extremely hard ultimate to use correctly, and it can be cancelled very easily by a lot of champions.
* Nunu & Willump's spell order is reliant on who he's laning with and laning against.
*Not a very good initiator.

Visionary: Every seven attacks, Nunu gets to cast a spell for free.

Consume: Nunu commands the yeti to take a bite out of a target minion or monster, dealing heavy damage to it and healing himself.

Nunu commands the yeti to take a bite out of a minion or monster, dealing 400/525/650/775/900 true damage to the target and healing himself for 125/180/235/290/345 (+1).

Cost: 60 Mana at all levels.
Range: 100.

Blood Boil: Nunu invigorates himself and an allied unit by heating their blood, increasing their Movement and Attack Speeds.

The heat of Nunu and a target ally's blood rises, increasing Movement Speed by 11/12/13/14/15% and Attack Speed by 25/35/45/55/65% for 15 seconds.

Cost: 50 Mana at all levels.
Range: 700.

Ice Blast: Nunu launches a ball of ice at an enemy unit, dealing damage and slowing their Movement and Attack Speeds for 4 seconds.

Nunu launches a ball of ice at an enemy unit, dealing 85/130/175/225/275 (+1) magic damage and slowing their Movement Speed by 20/30/40/50/60% and Attack Speed by 25% for 4 seconds.

Cost: 75/85/95/105/115 Mana.
Range: 550.

Absolute Zero: Nunu begins to sap the area of heat, slowing all nearby enemies. When the spell ends, he deals massive damage to all enemies caught in the area.

Nunu saps the area of heat, channeling up to 3 seconds, slowing surrounding enemy units' Movement Speed by 50% and Attack Speed by 25%.

Enemies caught in the area when the channel ends receive up to 625/875/1125 (+2.5) magic damage, depending on how long the spell was channeled.

Cost: 150 Mana at all levels.
Range: 550.

Visionary: A pretty great passive, especially when you use Blood Boil a lot. Every 7 attacks, you get a free spell, so if you're low on mana you can use this passive a lot, or just use Ice Blast every 7 attacks.

Consume: Consume is what allows Nunu to stay in lane forever, as well as making him a great jungler, even as an AP Caster. It deals true damage to minions (dealing more damage than smite at higher levels, with much less of a cooldown), and heals Nunu for a base amount plus Ability Power.

Use this ability when you get low on heath while laning, in team fights, and even use it while running away. Stopping for a second to heal all that health is worth it, and might even save your life.

Blood Boil: For just Nunu, the movement speed buff is great for chasing and running, and the attack speed is great for his passive. Leveling this up much (or at all) depends on your team and your lane partner. If you have an AD Carry, I'd level this up somewhat fast, as it helps them out a lot. An AD Carry laning with Nunu can forgo some Attack Speed for Attack Damage with Blood Boil.

Don't forget, you can use Blood Boil on minions, too!

Ice Blast: I love this spell. A great 1:1 Ability Power ratio nuke, as well as a slow for catching up to enemies or running away. It's a great harassment tool especially when it nukes squishy champions for a half of their HP.

Absolute Zero: This might be the hardest ultimate (in my opinion) to use in the game. Basically, Nunu channels a big circle around him, and all enemies in the circle are slowed and then take damage after a few seconds.

If your enemies are smart, they will run out of the circle, obviously. Or, any kind of Crowd Control can cancel it, really. Getting knocked in the air, taunted, stunned, etc. all screw up Nunu's ultimate. Some tips:

* Don't just run in and cast it, try to cut off escape routes. If they don't get hit by it, at least they're stuck getting smacked by your teammates.
* Cast from bushes. If they can't see you, they can't see the radius of the ultimate.
* It can be self-canceled. Just move. This is good if an enemy is about to go out of the circle, just cancel it and they'll take reduced damage, but still take damage.

Otherwise, just practice. One you get good, triple kills are easy to get with just your ultimate.

With 700 AP: (And assuming the enemy stays in the circle the whole time): You'll do 2875 damage, but that's true damage. With my build, you get close to that so... That one-shots a lot of champions.

As a caster, I level up Ice Blast as fast as I can, interrupting it with a point in Consume at level 2, and Blood Boil depending who I'm laning with.

Basically, the priority is going to be Absolute Zero, then Ice Blast.

But what about Blood Boil and Consume? Well, it depends. For Blood Boil, what's your team like? If you have some AD Carrys on your team but not in your lane, you don't really need this until laning is over, around level 10-14. If an AD Carry is in your lane, get this at level 3, and level up around your other spells.

For Consume, how are you doing in lane? At level 1, this gives great sustainability, but if you're against, say, two ranged champions, or just having a rough time, you might want more levels in Consume.

All in all, the skill sequence is definitely not set in stone by any means.

Marks (Reds):
Greater Mark of Magic Penetration is really the only option I feel can go in reds. Magic Penetration is great for just doing more damage with your abilities.

For alternatives, Greater Mark of Desolation is good for better jungling (but we're playing as an AP Caster here) and Greater Mark of Attack Speed for jungling and his passive. (But again, AP Caster, and Blood Boil helps with attack speed.)

Seals (Yellows):
Personally, I go with Greater Seal of Scaling Mana Regeneration. As a caster, Mana regeneration becomes a bigger and bigger issues at higher levels when we have cooldown reduction, constant blue, and are spamming abilities in teamfights.

Otherwise, some good alternatives could be Greater Seal of Armor for either Jungling or just early lane presence, or Greater Seal of Vitality for the extra health, which is always nice. But again, we're playing as an AP Caster here, so going with mana regeneration is good. In that case Greater Seal of Replenishment can be a good choice as well if you're having mana issues at earlier levels.

Glyphs (Blues):

I have two options that I consider mainly. Greater Glyph of Scaling Ability Power is a great choice for an AP Caster, that extra AP helps at later levels. Either that, or Greater Glyph of Scaling Magic Resist for the Magic Resist.

Some other options might be: Greater Glyph of Scaling Cooldown Reduction, for the cooldown reduction, Greater Glyph of Ability Power for straight up Ability Power at the early levels, or Greater Glyph of Magic Resist for early level laning and ganking. Otherwise, any caster-like Glyphs can go here.

Quintessences:
I prefer to use Greater Quintessence of Health because it gives a good amount of health to start with. That, or Greater Quintessence of Ability Power are my main two choices.

Some other choices are Greater Quintessence of Magic Penetration for the extra Magic Penetration (which I don't recommend because I get Void Staff Early), or maybe Greater Quintessence of Movement Speed for the speed to gank.

I go with 9 points in offense to hit Archaic Knowledge for the magic penetration. Standard for all casters.

Then I go with standard 21 points in Utility, making sure to hit 2 points in Utility Mastery since Nunu is great with Blue and Red. Nothing much to say here, just standard 9/0/21 caster masteries.

You could try some points in defense, like maybe 9/21/0 or 0/21/9, but I recommend the nothing special 9/0/21 caster masteries.

Personally, I go with Ignite and Flash. I love Ignite for the true damage which nets me a lot of kills or assists. And Flash is just a good summoner spell in general. As for the others:

Ghost: I wouldn't recommend since you have Blood Boil, but this is a good option over flash.
Cleanse: Cleanse is good because Nunu can't do anything against Crowd-Control.
Smite: Great for Jungling... But, this isn't a guide to jungling.
Exhaust: Sure. Exhaust then use your ultimate so they can't get away. But you also have Ice Blast's slow.
Clairvoyance: A good spell for support, but I'd leave this to someone else.
Teleport: If you're solo-laning, I'd probably take this spell. Otherwise, with Consume you should be able to stay in lane for a long time.

The bad ones:

Heal: Use Consume instead.
Revive: Useless.
Fortify: Leave this to the tank.
Clarity: Nunu does not rely on mana enough to use this, especially with Visionary.
Rally: Useless.

I'll just list all the items, and give my explanations for them.

Doran's Ring: A great starting item for any AP Caster. +100 HP is great at level 1, as well as the AP and the mana regeneration. If you want, you could also go with an Amplifying Tome to build into Mejai's Soulstealer if you so please.

Sorcerer's Shoes: For the extra spell penetration. I suppose you could build Mercury's Treads if you're having issues with Crowd Control or need the Magic Resistance.

Void Staff: The reason I build this as my first core-item is because you start to do almost true damage with your abilities which rocks.

Rabadon's Deathcap: Obviously a great AP item.

Rylai's Crystal Scepter: The HP bonus and the extra slow is great, and makes Nunu even tankier.

Abyssal Mask: Another good item, especially with the reduced Magic Resistance on enemy champions. With this, you're close to true damage.

Banshee's Veil: This can be replaced with another AP item like Mejai's Soulstealer, but it offers extra resistance, makes your more tanky, and blocks that nasty spell every 45 seconds.

I've always been a fan of early laning as any character, because it's a lot of fun.

Start out with buying either a Doran's Ring or an Amplifying Tome. I prefer a Doran's Ring because the 100 Health is great at level 1, as well as the Mana Regeneration and the Ability Power, which goes really far with Nunu's ratio. Then, pick up Ice Blast as your first spell and get to laning.

Now, I wouldn't recommend laning solo or mid, but if you do I'd still take Ice Blast at level one then immediately get Consume at level two so you can out lane whoever you're against.

At level one, you can obviously try for first blood (or try not to die first, anyways). Just go for minions and make sure you use Visionary to its fullest to get off some free Ice Blasts.

For levels 2-5, I'll make sure I have all my skills at level 1, unless your Blood Boil isn't useful at all. (Say, laning with another AP or maybe a support character) Then just constantly poke with Ice Blast everytime you can use it for free and make sure to use Consume when you need it.

Because of Consume, Nunu can tower dive, just make sure you have Consume up, because if you're able to eat a minion while running from a tower at low HP, you should survive.