This is my take on the Bird Man of Shurima, Azir.

Azir is a Mage, with his abilities scaling AP. What makes Azir unique is his auto attacking soldiers; auto attacking for Azir when he is in range, dealing aoe magic damage.

The reason why this champion should be picked over other mids is because of his kit. Azir excels at area denial and besieging bases. He is weak early game and usually cannot score kills without his team or use of his ult.

With an incredibly high skill ceiling and many combos and tricks to master, Azir takes a lot to get used to and master. I do not recommend playing him ranked without a minimum of 20 games as Azir in normals.

Pros

+ Late game powerhouse + Extreme zone control + Best passive in the game + Best disengage / CC ult + Great scaling + 3 AOE spells and escape + Nobody plays Azir. + Is a bird

Azir excels at controlling areas. His ult can lock people in jungle camps, block entire jungle pathways, and push people under towers. His soldiers deal AOE magic damage, hurting champs outside the target range. Believe it or not, a lot of people don't know how Azir works. People will use abilities on your sand soldiers, thinking they're like Heimerdinger's H-28G Evolution Turret, they attempt to dash through your Emperor's Divide and get knocked up again. This is a serious advantage, especially when they are killed by a resurrected turret they were standing around and looking at build.

Cons

- Glass cannon - No burst - Short range ult - Difficult to learn - Still buggy

Azir is still squishy even with crystal scepter and scaling health runes in the late game. Azir lacks burst, and instead relies on sustained damage. It's good in team fights, but count yourself out when it comes to 1v1 against an assassin mid lane. Azir's ult has incredible utility, but is extremely short range. His abilities are buggy and if you experience lag, Azir can be unplayable. Sometimes you soldiers don't attack, or your ult lets someone through. These glitches are frequent enough to be annoying, but are infrequent enough to confidently play ranked.

Azir suffers early, with his low base attack speed, low health, and lack of burst. Azir is built for the Late game.

I take Magic Pen marks , Scaling Health seals , flat Ability Power glyphs , and flat Ability Power quints .

Magic Pen Marks: Every mage will benifit from magic penetration.
Scaling Health Seals: Azir will need the survivability late game, when most assassins could take him down before you can ult them away.
Flat AP Glyphs and Quints: You may be wondering, well why not cdr glyphs or quints? Because our items put us at 40% cdr, which is the hard limit. overcaping on cdr is useless, while there is no cap on ap. Azir needs the ap early if he wants to get kills, or have his pokes do anything level 2. If you intend to farm up to the late game, Scaling ap quints and glyphs are a better choice.

I go 21-0-9 on Azir, which is standard for mid laners.

Offense: Make sure you use the Fury instead of Sorcery because over-caped cdr does nothing. Your soldiers count as spells, so take Expose Weakness over Spell Weaving . Arcane Blade plus the passive from Nashor's Tooth gives your basic attacks 20% of your AP as magic damage on hit, and full build you will have incredible attack speed. This will help you if you run out of soldiers.
Utility: Take Scout , as sometimes trinkets are difficult to place over walls. Instead of wasting your time trying to ward one spot, just take this mastery. The thicker walls at mid are sometimes difficult to put your trinket over, and Scout makes it easy. Its not worth messing around while Kha'Zix gets ready to jump on you from the bush. Azir is mana hungry if you mess up last hitting (which you will with this champ), so 3 in Meditation , and 1 in Fleet of Foot, to take us to the next tier. 3 in Summoner's Insight because you will need to Flash away like a little girl all the time, and 1 in Runic Affinity to make blue last longer for you.

The goal of these items are to fix 3 things on top of getting a lot of AP.

Max our CDR, for Azir's Passive, Shurima's Legacy
Have enough mana regen to be able to spam.
Be beefy enough to survive a team fight.

Instead of Luden's Tempest, you can get Zhonya's Hourglass if you're against AD or assassins.

Shurima's Legacy
Azir gains 1.25% bonus attack speed for every 1% of Cooldown Reduction. Additionally, Azir can place a turret on the ruins of another.
This is the most unique part of this champion. Your passive gives you massive attack speed with only 2 items. It's also it's own ability. Azir places a turret on the remains of another. In game, it is similar to using Thresh's lantern. Left or right click on the icon and after a short channel the turret begins a 5 second construction time. It deals physical damage based on a flat amount plus a percent of your current AP. The turret behaives like a normal turret, except gold earned by it is given to Azir. Your passive has a 3 minute cooldown that is unaffected by cooldown reduction, so don't waste it. Players unfamiliar with Azir think this part of your passive is your ultimate.
Conquering Sands
Azir relocates all of his active soldiers, dealing damage and slowing champions and minions they pass through.
This ability moves all soldiers, not just the ones in range. You can surprise enemies by hiding soldiers in a bush and using this ability to move them all at once. The first soldier that hits will damage and slow the target by 25%. Subsequent soldiers will deal 25% damage. The slow stacks additively.
Arise!
Azir summons a sand soldier to fight for him.
Soldiers deal AOE magic damage. They are not single target spells. Their attacks do not count as spell casts. Sand soldiers dance when Azir does, making Azir the only champion capable of a 1 man dance party. This is the bread and butter of Azir's kit, giving him the source of all of his damage. Azir's soldiers are similar to Heimerdinger's H-28G Evolution Turrets, as they attack for him. Unlike Heimerdinger's H-28G Evolution Turrets, Azir's sand soldiers have no health, are untargetable, and do not collide with units.
Shifting Sands
Azir dashes to one of his sand soldiers. Azir stops at the first enemy champion hit and knocks up the enemy champion. Azir additional gains a health shield upon colliding with the enemy champion.
This ability is an escape and initiation. Because it knocks up champions, it also interrupts channeling, like Karthus's ult, Requiem. Be careful not to initiate with this ability unless you can live for the time it is on cooldown. This dash ignores terrain, allowing Azir to dash over two walls if timed correctly. The dash, unless interrupted by a champion, will put Azir in front of his soldier. Make sure to use this positioning carefully.
Emperor's Divide
Azir sends forward a wall of shield bearing soldiers that knocks up and pushes back enemy champions.
The wall originates from slightly behind Azir. This is helpful when attempting to split up the enemy team or push your laning opponent into your tower. The wall is impassible to enemies, and will knock them up if they attempt to dash through it. Enemy champions can Flash and blink, like Kassadin's Riftwalk, through the wall.

Flash: This is the best summoner spell in the game. Why would you not take it?
Exhaust: I believe this summoner spell is more useful to Azir than other mid laners. Azir requires enemy champions to stand in range of his soldiers to do any damage. The slow and damage reduction from exhaust, plus its ability to remove stealth, like Vayne's ult, Rengar's ult, Teemo's passive, etc. makes this summoner spell the difference between dying and your opponent getting away, and taking minimal damage while effortlessly demolishing those affected.
Ignite: A good choice, but not helpful enough to beat Exhaust.
Clarity: Mana should never be a problem on Azir. His abilities are costly, but you won't be doing any all in fights unless you know you will score a kill. Do not pick Clarity.
Smite: You're not a jungler. Don't take smite. I don't care if you plan on buying Stalker's Blade, don't take smite.

In summary, Azir is a champion feared in the late game, with incredible skill required to play him effectively.

Please comment on what you think needs improvement and vote accordingly.