Before you even begin reading this build, it's important to realize that I'm not intending to make a tried and true, ultimate, competitive build. I'm a pretty casual LoL player, as far as League players go. Anivia is a champ that is very commonly played in ranked, but almost never in unranked. Although she can easily carry late game, Anivia isn't really considered to be OP'd by anyone's standards. If you're doing well with Anivia, you probably deserve it. I've played Anivia since season 2, when I started playing, and I used build her pretty differently than most players, mainly for the fact that I build heavily in the Utility tree, as opposed to the Offense tree (I also didn't use to have any magic pen :P). I appreciate constructive criticism, however, don't waste your time commenting if all you're going to do is complain about how I'm not following the meta, or something equally pointless.

A major thing to keep in mind with Anivia is that it's ok to not worry as much about your early game, and focus more on just getting fat (although don't ignore your team). She scales harder than most mages, and becomes a monster at full build.

OP: Overpowered
AD: Attack Damage
AP: Ability Power
MS: Movement Speed
MR: Magic Resist, magic defense
CDs: Cooldowns
CDR: Cooldown Reduction
AoE: Area of Effect
SS: Summoner Spell
HP: Hit points; health, life
MP: Magic points; mana
CC: Crowd control. League has a bizarre usage of this term. It doesn't mean dealing with a group of enemies, like in everything else. CC in League of Legends is equivalent to status effects (ex. poison, darkness, slow, etc.) in anything else.
DOT: Damage over time.

RoA: Rod of Ages
MFSB: Moonflair Spellblade
TotG/Tear: Tear of the Goddess
AAS: Archangel's Staff
Abyssal: Abyssal Mask
Witchcap: Wooglet's Witchcap
Deathcap: Rabadon's Deathcap
Torment: Liandry's Torment
Unholy: Athene's Unholy Grail
BFT: Blackfire Torch
Rylai's: Rylai's Crystal Scepter

TT: Twisted Treeline
SR: Summoner's Rift
3s: 3vs3; Twisted Treeline
5s: 5vs5; Summoner's Rift
Old 3s: TT prior to the total remodel on 10-25-12.
New 3s: The current TT, with Vilemaw, new items, etc.
"Glass": Little to no defense.

IMO: In my opinion
ATM: At the moment

If there's anything I missed, please let me know.

I've got Clarity as a suggested Summoner Spell, what could I possibly have to contribute to you, right? If that's your mindset, I'm surprised that you're even still reading this, but good on you, because you're learning from someone who values his own experiences above a meta that others have made.
I've been playing Anivia since season 2, when I first began playing League of Legends. She's been my main from the beginning. I've seen numerous changes to the game with her. I've played her in multiple roles. I've personally experimented and played for many, many hours with her, trying new things. Mainly using my own ideas and what's worked for me, and sometimes looking at others. When I detail something in this guide, it's from many personal experiences, and not emulating what (insert professional-level player(s) name(s) here) have done. I've adapted, and generally, succeeded.

Anivia's extremely fun to play most of the time, despite some glaring weaknesses.

Strengths
Extremely good burst damage
You scale harder than almost every other champ in the game
One of the best farming and pushing abilities in the game, Glacial Storm
Good range on basic attack and Q
Low CDs (except for Crystallize and early levels of Flash Frost)
Doesn't have to be carrying to benefit the team
Good CC and AoE
This is a "one size fits most" build
Very tanky for how strong she is at full build (especially compared to other mages)
Borderline OP on this map*
Wall ( Crystallize) can force 1vs3 situations if placed properly: It can block off the entire top lane at max rank (also grants sight)

*At full build. Some champs just beat her, period, however, against most champs, she's unbelievably good. Also, her walls in this map's jungle are ridiculous.

Weaknesses
Extremely squishy early-mid game
ZERO Tenacity ( Moonflair Spellblade is a very welcome addition!)
Extremely vulernable to ganks early game
Very hard to farm pre-level 6
Very mana hungry early game
Easily countered*
Slow if not built properly
Spellvamp is basically pointless on her
Almost no physical damage: basic attacks extremely slow and weak
Low MR for awhile

*By simply getting MR; doesn't mean people do it. Banshee's Veil is pretty much an instant counter.

Anivia's main stat is AP, as all of her skills scale with it. Also, Anivia is extremely vulnerable to ganks, especially at lower levels when you don't have completed boots, and higher leveled skills to slow/stun/block your attackers. Anivia is both one of, if not the, squishiest and slowest champ in the game. Armor is important in general, especially for Anivia, who has low armor, and can easily be crushed by AD-heavy champs if not careful. The extra armor'll help you survive longer. The AP, again, is self-explanatory.

Acceptable Marks
Greater Mark of Magic Penetration: I used to use Greater Mark of Armor, since they give you about as much armor as these marks do magic pen, but that's building Anivia a bit too tanky for her role, so I switched my marks in favor of a higher damage output. I also used to use Boots of Swiftness as opposed to Sorcerer's Shoes. I've played Anivia in numerous ways in the past, so trust me when I say that magic pen is almost mandatory for her.
Greater Mark of Hybrid Penetration. These marks give you greater harassing ability during the laning phase at not a huge loss in magic damage. I simply don't prefer them on this map because laning doesn't generally last as long.

Acceptable Seals
Greater Seal of Scaling Armor: You have usually have time to get the scaling on these on this map, and they obviously provide better stats.
Greater Seal of Armor. These are also solid choices, however, you level so quickly on this map, and you don't often face a physical damage dealing champ, so you usually have ample time to get the scaling before you notice the lack of early game armor.

Acceptable Glyphs
Greater Glyph of Scaling Magic Resist: Now that I don't get any MR items, I take these glyphs. I've had much more success with these than with AP glyphs. Also, by no longer getting Athene's Unholy Grail, I start to really hurt much earlier.
Greater Glyph of Magic Resist. I would never take this in blink pick. Maybe if you had a second page for it in ranked, and you can see that you're up against Fizz or Annie, but otherwise, I can't recommend these.
Greater Glyph of Scaling Ability Power. If you took these, I'd STRONGLY suggest that you get Abyssal Mask immediately after Rod of Ages, but this delays your Wooglet's Witchcap, so again, I can't recommend it.

Acceptable Quints
Greater Quintessence of Movement Speed: These are a matter of preference. When using Sorcerer's Shoes, Anivia is simply too slow to secure most kills, or escape from lethal combat. Using these quints makes those much easier while still getting the magic pen from the boots. Personally, if you don't have at least 400 MS, you're too slow, period. Anivia gets just about exactly 400 MS if you get all three points of Fleet of Foot , a single Greater Quintessence of Movement Speed, and Sorcerer's Shoes - Alacrity. The starting MS, however, without boots (assuming you start with a Doran's Ring) is only 335. This is unacceptable to me.
Greater Quintessence of Ability Power. If you're ok with being slow as hell, feel free to use any number of these. They're powerful, but MS is valuable at all stages of the game. 20 AP (15 + 30% from Wooglet's Witchcap and Archmage ) becomes almost completely irrelevant by the end.

Your main goal as far as stats are concerned is to hurt. You want AP, CDR, mana regen, etc. Basically, you wanna hurt, hurt often, and hurt for extended periods of time.

Explanations
Sorcery: CDR is extremely important in 3s, especially for a mage. In 3s, you need to be able to do more than simply deal sh*t loads of damage then die. You should be able to kill enemies without dying. Without CDR as a mage, you use your spells, then literally do nothing while you wait for them to come off of CD. You wanna be able to use spells frequently. All of that being said, Anivia doesn't scale as well with CDR as say Maokai, since she has low CDs (at least at higher levels).

Expose Weakness : This suits my playstyle, but it's also useful for getting deeper into the tree. I suggest staying away from Double-Edged Sword as a mage or a tank. As a mage, you already hurt a lot, and the extra damage doesn't help you as much as the negative side of the mastery hurts you. As a tank, you don't hurt enough to justify taking more damage.

Mental Force : Nothing surprising or deep here, it's AP.

Arcane Mastery : Again, nothing exciting here. It's a nice boost to your early game (this is more AP than a flat AP quint).

Executioner : This is useful for ensuring that your second combo is the last one that you need (obviously, you won't be engaging the more durable targets alone).

Archmage : I trust that you can figure this one out.

Fleet of Foot : Easily my favorite mastery of the season. Everyone should've had access to MS since the beginning of League of Legends, and now they finally do.

Expanded Mind : Anivia's extremely mana hungry, so every bit of MP helps.

Summoner's Insight : Shorter CDs for Flash, Clarity, and Teleport.

Strength of Spirit : I personally love having health regen, regardless of the champ. This is just enough to say that you have some, which is fine by me. Very justified for a single point.

Greed : More gold (even a small amount) is nice for someone so item dependent in order to deal damage.

Meditation : This is exceedingly welcome, as it's a mini- Chalice of Harmony Mana Font at all times. In 3s, since you already have increased MP regen, this allows you to skip a second MP item ( Archangel's Staff/ Athene's Unholy Grail) in favor of getting stronger faster.

The main portion of the build. Items are the single biggest game changers. If anything is confusing as to why I get the items I do, feel free to ask, however, I believe that the items're fairly self-explanatory.

Sorcerer's Shoes - Alacrity: No questions asked, these boots are a must. Trust me, I used to use Boots of Swiftness as I was learning in season 2, and the magic pen is mandatory. As for the enchantment, nothing else makes sense on TT... for anyone. I really like flat (noticeable) bonuses with no conditions, not to mention, nothing else really helps (especially compared to this).

Rod of Ages: Absolute core on Anivia. Anivia benefits from health more than most mages, due to her essentially double-dipping with her passive. She's also extremely mana hungry, and this gives you more mana, as well as a nice passive for staying in lane. There is absolutely no acceptable excuse for not rushing* this every single game.

*You may get Boots during the process if you don't enough gold for the Blasting Wand or the recipe itself, if you don't start with them.

Wooglet's Witchcap: Nothing surprising here. Tremendous AP, a decent amount of armor, very cool. Also, it gives you a nice statis active, which can be used to double troll/bait while your spells are on CD, making you even harder to kill. Sometimes it'll even work in your egg, making you invincible as Rebirth is taking place.

Rabadon's Deathcap: DAMAGE!!!

Liandry's Torment: This is an excellent choice for Anivia. More magic pen is never bad, nor is health. The passive on this item will always proc the double damage effect on Anivia, since Chill slows, and both spells that Chill are used anytime Anivia deals damage.

Luden's Tempest is the perfect way to finish off your build. It makes you even faster and stronger, and the build path is pretty good.

Abyssal Mask: A great choice if you need some more MR. It provides excellent AP, essentially 20 more magic pen (since Anivia's range is within the range of the aura), and some more defense against enemies with magic damage. You'll almost always get this (unless the enemy team has literally no magic damage).

Moonflair Spellblade is a fantastic item. It gives you great defense in every form except for health (which you already have a decent amount of for how strong you are). As much AP as Torment, 50 armor (even more than Witchcap), 50 MR (as much as Abyssal), AND tenacity. Even so, MFSB isn't nearly as useful for Anivia as it is for Maokai, so don't expect it to be your end-all solution for her. Generally, the only CC that really messes with Anivia isn't mitigated by tencacity, so keep that in mind if your main goal behind getting this was for that.

For SR, you need a second item for MP after RoA. The best bet is usually Archangel's Staff, but Athene's Unholy Grail is also great. If you're still learning Anivia, I suggest this. It makes things a lot easier and quicker at the expense of damage.

Do not get Void Staff. There's almost never a reason to. If you're debating it, exhaust all other possible options first.

Welcome to the highest-rated guide on all of MOBAFire that uses Clarity.
Flash/ Clarity
Why Clarity? Simple. In TT, you have extra mana regen, and it takes less exp to level up, so between Clarity, Catalyst the Protector's passive, your base mana regen, and the extra from being on TT, you don't need to get mana regen items. In short, why take Clarity in 3s? Take Clarity because it's 3s. On TT, it's a spell worth 2700 gold.

As for SR, the choice depends on your position. If you're support, it's obvious. You either take Exhaust to help your marksman, or you take Heal if they don't take it themselves.
Mid laners typically love to take Ignite, but I'm not at all a fan of that spell, unless you also have other forms of DOT ( Darius, Teemo, etc.), in which case, it's pretty awesome. Anivia, however, has no DOT. Teleport is nice for split pushing, which Anivia is actually really awesome at thanks to Glacial Storm. The main reason that I take it, however, is because of Eggnivia Teleporting. If you're unfamiliar, I'll introduce you to one of the main reasons why you don't care about laning Zed.

Teleport ("TP") is a less straightforward spell than it seems like. TP has a long channel, so one of the biggest things to watch out for when using TP to escape is getting stunned, ensnared, or otherwise becoming immobilized. This includes silences and fears. If you get hit with Unstoppable Force or something like that, the channel stops. Note that slows won't stop you. The key to Eggnivia TP is knowing when to use it. Since you can't cast anything as an egg, the way it works is to start TP as a bird. TP doesn't stop when you turn into an egg. The only way it stops is if the channel gets interrupted. As long as this doesn't happen, you'll freely leave the fight. So why does this help against Zed? He has no CC aside from one slow. He can't do anything to you unless he can kill your egg from full HP in less than three seconds. Since this is extremely unlikely, it effectively counters him in lane. Also, for this reason, I recommend trying to save Teleport for when your egg is up. If your passive still has a long CD remaining, feel free to TP, but the main reason that you're taking the spell is to have a safer laning phase.

During the laning phase, only use your ult for clearing minion waves, and for tagging champions with chill, then hit them with an E. Your ult doesn't provide a lot of damage at early ranks, but it grants you a lot of utility: AS and MS slow, Chilling targets, farming, and zoning.

Anivia has little variety in terms of offense. You basically do the same thing with her in almost every situation, against almost every champ. Her all-in combo is as follows:

You can use your wall during this to make it easier to use your other spells, but that isn't involved in the actual damage, so I'll omit it.

Start with Glacial Storm around the victim, followed by Flash Frost, making sure to hit with both parts of the Q, then finally, land a Frostbite. This is a devastating combo, especially against squishies without tenacity.

Damage: 914 ( Flash Frost) + 904 ( Frostbite) + 299 ( Glacial Storm) per second* = 2117 + 299/sec
Mana cost: 210 ( Flash Frost) + 90 ( Frostbite) + 75 ( Glacial Storm) + 60/sec* ( Glacial Storm) = 375 + 60/sec
CC effects: 3 sec MS slow (20%), 1 sec stun, 20% MS & AS slow per second*
*The duration is dictated by how long they stay in your ult

As a mage, support Anivia has similar strengths and weaknesses to her usual self. For starters, she's much squishier than a tank support like Thresh, Braum, or Leona, but she brings long-range and high utility to bot lane. Here, I'll list a few of support Anivia's high and low points.

Pros
High range (600 on basic attacks, even higher for spells)
High damage potential, although, only average base damage
Excellent utility (only surpassed by a few champs in the entire game: Maokai, Blitzcrank, Thresh, Leona, Alistar), which allows her to peel very well for her marksman
Works well with most marksmen, especially with Vayne for Condemn + Crystallize
Doesn't require support item upgrades (ex. Frostfang, Frost Queen's Claim), so she can get straight to Sightstone, and then to her bird core

Cons
Still extremely mana hungry
You'll be even slower to get Rod of Ages since you have to get Sightstone first
Relatively squishy, although her egg can cause a distraction for her marksman to escape, if need be. Also, she's much tankier than most of the other mage supports (*cough* Nami *cough*)
No direct buffs or healing to her marksman or herself

I hope that if you've made it through this build with an open mind, you can at least see where I'm coming from. Thank you for reading, and I hope that this guide at least helps a few people pick Anivia up to make their own builds.

I frequently update my guides, so expect periodic changes.