Hey guys, I'm a friendly League Player by the username of JumpScareNova, NA. I'm an Anivia main, and I've been playing her since I picked up the game in Season 5. With this guide, I don't intend on miraculously transforming you into a super enlightened Anivia one-trick. In fact, I am catering more towards the newer players (pre-level 30 or less than a season of experience) and those who are looking to pick up Anivia as a new champion or secret pick. If you wanted to learn how to play Anivia like a Diamond-Challenger level, then I doubt you'll learn anything new from me and I would recommend you check out some big names such as Froggen to watch and learn from as they can explain and show you how Anivia's strengths and weaknesses fit into the meta and against higher skilled players. I haven't finished this guide to the fullest extent that it could be, so please bear in mind the gaps (Example, the Champion Match-Ups). If you feel that I have missed something, feel free to tell me! I hope this helps you find out if you like Anivia and I wish you the best playing the Immortal CryoPhoenix and daring that Zed to tower dive you. I did take the time to put in some notes, so if anything confuses you, maybe the notes would help!

Anivia is like most champions, they have some unique/semi-unique specific traits and abilities in their kit that allows them to be dynamic in the way each game is played. The most important ability in Anivia's kit is her ultimate, Glacial Storm. Her ultimate provides reliable, consistent damage towards your opponents in a large area while also significantly slowing their movement speed. As her ultimate is a channeled ability over a set area, being able to fight around her ultimate and manipulating your opponents to fight in it is a key trait to being successful on the Rift. While it can serve as a strong tool for area control, it also can clear waves with ease and enables a powerful control playstyle.
While her ultimate is the most important ability to be able to use well, the most powerful and unique ability in Anivia's kite is her ability to create temporary terrain on the map with her W, Crystallize. This ability creates a wall that scales in length with ability ranks and can be used to block off escape routes in a fight and can be used to catch/trap opponents. In addition the casting of her W can act as a pseudo-crowd control ability as the summoning of the wall can briefly displace any units standing on where the spell was cast, which can prove to be really useful to cancel channels such as Vel'Koz's ultimate abilirt or the enemy's (or ally's) recall back to base. If you're really cool, then you can also use Anivia's wall to interrupt enemy dashes by timing its cast in the middle of their dash. The biggest sign of an experienced Anivia player is how they use their wall, as the simple ability has the power to create so much impact. One wall can deny so much if used well: moments like the jungler's slight overextension turning into a game-winning catch, the enemy team's slow grouping leads to your wall separating their team and giving your team the edge to dominate the fight, and more.
Although the wall has the power to make some awesome plays, it can also easily be the reason for something going wrong. One mistimed wall can cause that game-winning catch to slip away from your team, or that perfect divide in the enemy team to turn into a split in your team.
With these two powerful control abilities making up half of Anivia's kit, Anivia has two simple damaging abilities. Her Q - Flashfrost, is an AoE skillshot that causes enemies hit by the ability to be slowed, and those hit by its detonation to be stunned. Her E - Frostbite is a point and click ability that deals double damaged to those recently stunned by her Q or damaged by her ultimate and has a fixed, short cooldown. With the use of her ultimate and wall, Anivia's ability to land her Q and empower her E gives her one of the most powerful area control playstyles in the game.

With the new Season 8 Runes/Masteries combination, I've found that there are only really two main keystones that have synergy with Anivia's kit. As I already listed the main rune page, I will be discussing the details behind the most important runes and the less common rune page.
The first (and most popular) is the one shown here - the Sorcery Keystone called Arcane Comet. Out of all the different rune trees, Sorcery is the most beneficial to mage-like champions as it provides flat ability power and excellent runes to assist in mana sustain and scaling. Anivia is one champion that benefits greatly from the Sorcery tree, as her mana sustain is significantly improved with Manaflow Band and her ability to stall games makes Gathering Storm more powerful. If you choose to not take a Sorcery Keystone, I would highly recommend taking Sorcery as the secondary tree to take advantage of the benefits from Manaflow Band and Gathering Storm.
The second Keystone that Anivia can synergize with is the Inspiration Keystone called Unsealed Spellbook. Unsealed Spellbook is a harder to use keystone as it has more complications than simply adding more damage to your abilities. Unsealed Spellbook allows Anivia to have two main advantages: To always have at least one summoner spell available and to be able to change how you play. As Unsealed Spellbook allows the player to take additional summoner spells, you can take ignite to gain kill pressure on your opponent who had recently used their Flash Summoner Spell, or to take Ghost to assist in kiting the enemy team in a teamfight, or to take Exhaust to save yourself or a teammate from sudden burst, or cleanse to save yourself from a life-ending crowd control from locking you down. As Unsealed Spellbook is a more macro/playstyle dependent keystone, it can get really confusing or be really hard to utilize in actual gameplay. However, when used effectively, Unsealed Spellbook can provide Anivia with numerous advantages. For the non-keystone runes in the Inspiration Tree, I would recommend Perfect Timing, Biscuit Delivery, and Time-Warp Tonic as the primary tree setup and a sorcery secondary tree with Manaflow Band and Gathering Storm. The Inspiration rune choices are catered towards sustain and being able to stay in lane and farm as Anivia is weaker than most champions prior to Level 6, and stuggles with mana issues prior to completing Rod of Ages and Archangel's Staff. Feel free to switch up the runes based off preference or matchup, but I wouldn't recommend ever taking Hextech Flashtraption in any case.

Pros:
-Lots of Crowd Control in her kit
-Second Life in a Bottle (Passive)
-Late Game Monster
-Excellent Controlling Capabilities
-Lots of AoE
-High Skill Ceiling - Anivia has plenty of room to show skill expression.
-Does not have any super-long cooldowns that most champions have - Ultimate CD is only 6 seconds.
Cons:
-Anivia isn't the easiest champion to play, despite the simplicity in some of her abilities.
-She can be her own reason to lose lane - Anivia has a slow auto attack, so last hitting with it under tower is extremely difficult and leads to mana expenditure or lost gold.
-Anivia's only skillshot is slower than most skillshots. If it's going to hit, it's going to hit.
-Managing Mana early-game is a must and messing it up can lead to massive punishments
-Anivia is REALLY slow. Anivia has a lower than normal base movement speed, so getting caught really means you got caught. Especially since Anivia has no escapes in her kit.
-Doesn't have the most aggressive style of a mage in the game. Her cooldowns are long early game and runs out of mana really quickly.
-Low starting health - Yes there is her Passive, but it's not every death you have a chance to come back. Losing the passive can be very easy and cause a lot of things to prevent you to do well.
-Anivia's E (Her Nuke) is also a slow-moving projectile. If the enemy opponent escapes from your ultimate or puts enough distance from you before your E can land, there is a good chance it won't do double damage.
-Can't kite backwards or forwards as effectively as other champions. If you need to move your ultimate mid-fight, you have to wait 6 seconds for the cooldown to come back up and then 1.5 seconds for the ultimate to reach max size.

I hope this Guide was useful to some extent, and sorry if you thought it was a bit corny. I didn't want to be long and boring. Perhaps maybe you, the one reading this, will pick up Anivia? Heh heh. It won't hurt my feelings if you don't like Anivia or if my guide was confusing in any way or unhelpful or poorly made. Anivia does have her bad match-ups and is generally a harder champion to get good at, so losing to a simpler opponent like Annie can be frustrating. However, that river can flow both ways. A bad match-up can be good for Anivia if you work around the strengths Anivia has anad the weaknesses of whatever nightmare match-up you thought you had in the loading screen. Every champion can be built to suite each player's preferences and this is just my preferred way to build her and I hope others will also enjoy this style was well. Thank you for taking the time to get this far in the build and I would appreciate any comments/feedback you could give.