This chapters has been copied from http://leagueoflegends.wikia.com/wiki/Aatrox

I don't own anything, No Company Infringement Et. Al.

All credits goes to this site:
http://leagueoflegends.wikia.com

Aatrox is a legendary warrior, one of only five that remain of an ancient race known as the Darkin. He wields his massive blade with grace and poise, slicing through legions in a style that is hypnotic to behold. With each foe felled, Aatrox's seemingly living blade drinks in their blood, empowering him and fueling his brutal, elegant campaign of slaughter.
The earliest tale of Aatrox is as old as recorded history. It tells of a war between two great factions remembered only as the Protectorate and the Magelords. Over time, the Magelords won a series of crushing victories, leaving them on the brink of obliterating their sworn enemy forever. On the day of their final confrontation, the Protectorate army found themselves outnumbered, exhausted, and poorly equipped. They braced for inevitable defeat.
Just when all hope seemed lost, Aatrox appeared among the ranks of the Protectorate. With but a few words, he urged the soldiers to fight to the last before throwing himself into battle. His presence inspired the desperate warriors. At first, they could only watch in awe as this unknown hero cleaved through their enemies, his body and blade moving in unison as if one being. Soon, the warriors found themselves imbued with a potent thirst for battle. They followed Aatrox into the fray, each fighting with the furious strength of ten until they had won a most unlikely victory.

Aatrox vanished after that battle, but the Protectorate army's newfound fury did not. Their surprising triumph led to many more until they were able to finally return home victorious. Their countrymen hailed them as heroes, but though they had saved their entire civilization from destruction, darkness lingered in the mind of each warrior. Something within them had changed. Over time, their memories of battle faded, only to be replaced with a grim revelation: their acts of heroism were, in fact, brutal atrocities committed by their own hands.

Tales like these appear among the myths of many cultures. If they are all to be believed, Aatrox's presence has changed the course of some of the most important wars in history. Though these stories remember him as a savior in dark times, Aatrox's true legacy may be a world filled with conflict and strife.

"Some fight for honor, some fight for glory. It matters only that you fight."
―Aatrox

Credits: http://leagueoflegends.wikia.com/wiki/Aatrox/Background

Blood Well(Innate): Aatrox stores a portion of his abilities’ health cost in the Blood Well, which slowly drains to a base amount while he is out of combat. When Aatrox loses all of his health, he draws on the Blood Well and recovers the amount of health stored.
Whenever Aatrox uses an ability that costs health, he stores 100% of the health cost into his Blood Well. The maximum amount of health the Blood Well can store is equal to 30 + (45 × level). If Aatrox has not dealt or received damage in the last 5 seconds, his Blood Well will deplete at a rate of 2% per second.
Upon taking fatal damage, Blood Well activates and places Aatrox in stasis for 3 seconds. Over the stasis duration the Blood Well is emptied and Aatrox restores health equal to its contents plus 10.5 + (15.75 × level). Blood Well's activation has a static cooldown and is unaffected by cooldown reduction. Also, Aatrox passively increases his attack speed by 1% for every 2% in the Blood Well.
The bar under his health is the amount Blood Well Aatrox has.
If the Blood Well is red: Blood Well is active, if the Blood Well is white: Blood Well is on cooldown.
Blood Well also appears as a buff icon.
Blood Well's restored health is affected by Spirit Visage's unique passive.
Guardian Angel will take precedence over Blood Well.
Aatrox is cleansed of all forms of crowd control and damage over time (with the exception of leashes) once he enters stasis.
Commanding Aatrox to move during the stasis will cancel the spell and lower the health restored.

-x-x-x-x-

Dark Flight(Active): Dark Flight is a ground targeted area of effect ability. Aatrox takes flight and slams down at a targeted area, dealing physical damage to nearby enemies upon landing. Enemies in the center of the area are also knocked up for 1 second.
Range: 650
Cost: 10% of current health
Cooldown: 16 / 15 / 14 / 13 / 12 seconds

Physical Damage: 70 / 115 / 160 / 205 / 250 (+ 60% bonus AD)

When Aatrox activates Dark Flight he will 'fly' to a selected area. He will damage the enemies that are in the area where he lands. He will knock up the enemies in the center for 1 second.
Dark Flight does not proc on-hit effects.
Dark Flight procs spell vamp and Rylai's slow similarly with all Area of Effect spells and abilities with diminished effect.
Dark Flight pops spell shield.
Dark Flight will not damage Black Shield and the knock up is negated.
When Aatrox is in the air, you can still hit him.
Dark Flight can be cancelled by knocking up or killing Aatrox while the animation is in progress.
Dark Flight does not cancel other commands. Aatrox will immediately begin attacking after he lands.
With smartcast on, Dark Flight will be cast immediately and at 650 range if the cursor is beyond that.

Blood Thirst(Toggle Off): Aatrox heals himself on every third attack. If Aatrox is below 50% health he will heal for three times as much.
Cooldown: 0.5 seconds
Heal: 20 / 25 / 30 / 35 / 40 (+25% bonus AD)

Heal below 50% health: 60 / 75 / 90 / 105 / 120 (+75% bonus AD)


Blood Price(Toggle On): Aatrox deals bonus physical damage on every third attack at the cost of health.
Cooldown: 0.5 seconds
Bonus Physical Damage: 60 / 95 / 130 / 165 / 200 (+100% bonus AD)

Health cost every third attack: 15 / 23.75 / 32.5 / 41.25 / 50 (+25% bonus AD)

Blood Price/Blood Thirst is an ability that Aatrox can toggle to heal himself or deal extra damage every third attack.
The on-hit effect of Blood Price does not proc life steal or spell vamp.

Blades of Torment(Active): Aatrox unleashes and sends forward the power of his blade, dealing magic damage to enemies in a line and slowing them by 40% for a few seconds.
Range: 1000
Cost: 5% of current health
Cooldown: 12 / 11 / 10 / 9 / 8 seconds

Magic Damage: 75 / 120 / 165 / 210 / 255 (+ 60% AP)

(+ 60% bonus AD)
Blades of Torment is a Conic area of effect skillshot that damages and slows enemies in the area it hits. The area of effect will gradually get narrower nearing end of Aatrox's Blades of Torment range.
Blades of Torment does not proc on-hit effects.
Blades of Torment procs spell vamp and Rylai's slow similarly with all Area of Effect spells and abilities with diminished effect.
Blades of Torment pops spell shield.
Blades of Torment will damage Black Shield and the slow is negated.

Massacre(Active): Aatrox draws in the blood of his foes, dealing magic damage to nearby enemy champions.
For the next 12 seconds, Aatrox gains bonus attack speed and 175 bonus attack range. His attacks are still considered melee.
Bonus Range: 175 (total range - 325)
Cooldown: 100 / 85 / 70 seconds
Magic Damage: 200 / 300 / 400 (+100% AP)

Attack Speed: 40 / 50 / 60 %

When Aatrox activates Massacre his sword is longer.
Massacre does not proc on-hit effects.
Massacre procs spell vamp and Rylai's slow similarly with all Area of Effect spells and abilities with diminished effect.
Massacre pops spell shield.
Massacre will damage Black Shield.
Actual hitbox of Aatrox's Massacre is bigger than the particle effect itself.
Unlike Kayle's Righteous Fury, Aatrox's Massacre does not classify him as a ranged champion, effecting Tiamat / Ravenous Hydra and Runaan's Hurricane as a melee champion would.

Credits: http://leagueoflegends.wikia.com/wiki/Aatrox/Ability_Details

Top-lane
The sustain from Blood Thirst keeps Aatrox's health topped off, allowing him to farm throughout the laning phase. Aatrox excels as a duelist, able to switch to Blood Price for heavy burst damage when trading with his lane opponent. After the exchange, Aatrox can toggle back to Blood Thirst to top off his health. When he’s ready to finish the job, Massacre adds significantly to an already potent burst combo.
If the lane isn't going Aatrox's way, the knock-up effect from Dark Flight can be used to set up ganks for his jungler. Or, if Aatrox has bullied his enemy out of lane, he can push aggressively, safe in the knowledge that the disengage from Dark Flight and Blades of Torment’s slow will aid his escape when enemies come charging. Even when things go totally wrong, Blood Well offers a second chance to secure kills or make a quick exit.

Team fights
Aatrox's mobility gives him an innate ability to pressure enemy carries in team fights. Blood Thirst grants Aatrox plenty of sustain as he tangos with enemy initiators and tanks. When he sees an opportunity to reach an enemy carry, Dark Flight closes the gap and allows the punishment to begin. When Aatrox is in deep, the area of effect burst and extra range from Massacre, and slow on Blades of Torment prevent high-value targets from escaping. All the while the consistent healing from Blood Thirst and resurrection effect from Blood Well keep him alive long enough to cut through enemy squishies.
If Aatrox's team is on the defensive, a well-aimed Blades of Torment can slow multiple enemies and open a window for retreating allies to slip away. Alternately, he can kite enemies with Dark Flight, and create an opportunity for the remainder of his team to turn and counter-initiate. If Aatrox is focused, Blood Thirst's sustain and the Blood Well keep him in the fight, giving his teammates an opportunity to cut through foes as he resurrects and delivers the killing blow.

Dark Flight can be used as both an initiation move and a disengage, but be aware that Aatrox is still vulnerable to crowd controls, such as stuns and knockups.
Blades of Torment and Dark Flight have some synergy with each other.
Using Blades of Torment first can allow you to get in a few hits and hopefully force an enemy to attempt an escape, after which you can follow up with Dark Flight for further punishment. Reversing the skill order will achieve the same effect but not with the same efficiency - Dark Flight has a longer cooldown and is a "harder" form of crowd control, thus encouraging more efficient use.
Try following the bonus damage from your Blood Price immediately with Massacre after you engage for the quickest burst of damage. A full combo would be readying your Blood Price, engage with Dark Flight, proc Blood Price bonus damage, then activate Massacre to deliver a burst of damage.
Be aware that both Blades of Torment and Dark Flight briefly interrupt Aatrox's movement.
When trying to disengage, it's good to use Blades of Torment first (since it has a longer range and a shorter cast animation) followed immediately by Dark Flight (since it has a shorter range and a longer cast animation).
With enough life steal, Aatrox can leave Blood Price on indefinitely, as the amount of damage he takes every third strike is negated by the life steal.

Credits: http://leagueoflegends.wikia.com/wiki/Aatrox/Strategy

Aatrox is a melee fighter who specializes in strong initiation and in-fight sustain. As a health-based caster, Aatrox relies on dealing heavy damage to stay alive.
Damage
Aatrox benefits from life steal since it allows him to negate the health loss from his abilities.
Apart from life steal, Blade of the Ruined King provides attack speed, letting him regain insane amounts of health through Blood Thirst. An early Bilgewater Cutlass also gives some much-needed early sustain.
The Bloodthirster is the item that gives the most attack damage and life steal in the game. It will make Aatrox extremely potent in 1v1 duels.
Ravenous Hydra is a very useful item to have when in the middle of a teamfight, allowing you to both deal damage to and heal from multiple enemies, giving Aatrox a very powerful late-game presence.
Trinity Force provides many valuable stats to Aatrox, giving movement speed, attack speed, health, attack damage, and a Phage movement speed bonus on-hit .
Aatrox can use all 3 armor penetration items effectively ( Last Whisper, The Black Cleaver and Youmuu's Ghostblade). The choice depends on whether or not you need armor penetration early, and also whether or not your enemies are focusing on armor.
If you predict that your enemies are likely to get high amounts of armor, it is best to get Last Whisper during mid-game, helping you transition into your late-game phase better due to the high armor penetration and low cost.
If you feel that you need armor penetration more early, or that you need cooldown reduction, getting a The Brutalizer is a good idea. It can later be upgraded into a The Black Cleaver, which offers high armor penetration and some useful health, or Youmuu's Ghostblade which offers a passive that synergizes fantastically with Aatrox, as well as some critical strike chance.
Zephyr gives off great offensive stats, and the tenacity is good if not getting Mercury's Treads.
Health
Sunfire Cape's passive will allow Aatrox to deal mixed damage, forcing enemies to itemize on some magic resist as well as armor.
Randuin's Omen helps soak up damage in team fights and helps you survive long enough to take out high priority targets and the active slow helps catch running enemies.
Spirit Visage in conjunction with Ravenous Hydra results in fast healing due to the increased healing affects of Spirits Visage and the AoE life steal from Hydra. It also sync well with his Passive and Blood thirst as it also increases their healing.
Frozen Mallet is also a good choice since it provides 700 bonus health and a on-hit slow.
Boots
Mercury's Treads are essential against teams with high crowd control and/or magic damage. As mentioned previously, Zephyr can replace this item if there is a lack or magic damage but there still are large amounts of CC.
Ninja Tabi offers an upgrade path to Cloth Armor, and the passive helps to trade against AD champions and freeze the minion wave.
Resistances
Guardian Angel is equivalent to a second Blood Well; they both revive Aatrox after death. This gives more survivability and allows for more opportunities to finish off targets.
Guardian Angel's passive procs before Aatrox's passive, so you'll keep the attack speed granted by Blood Well after your first revive.
An early Hexdrinker is primarily to counter laning opponents dealing mostly magic damage. Additionally, the active shield can save Aatrox from an otherwise untimely death.
It can later be upgraded into a Maw of Malmortius. The closer to death Aatrox is, the more attack damage granted by the unique passive of the item.

http://leagueoflegends.wikia.com/wiki/Aatrox/Strategy

When Aatrox takes fatal damage he is healed for the amount currently in his resource bar. Landing a fatal blow on him while the resource bar is low will result in him reviving with a lower amount of health.
Unlike other reviving champions, Aatrox's Blood Well revive is rapid and grants him invulnerability during this time which allows him to quickly rejoin a team fight after being dropped to critical health.
When fighting him, consider his resource bar as part of his own health. (For example, killing him with a full Blood Well will make him return with a large portion of his hitpoints and if the fight was closely matched, he will most likely kill you.)
Be aware that his passive (after reviving) doesn't provide any attackspeed anymore, because he consumes all the blood within it and be sure to look if he got the Blood Thirst/Blood Price buff while reviving.
When Aatrox casts Dark Flight towards your location, avoid being knocked up by moving away from the center of impact.
Most players will aim the ability right above you or right behind you. So, moving closer to Aatrox at the time he casts Dark Flight will likely make the skill miss you.
In lane, zoning Aatrox out of combat will quickly drain out his Blood Well making him a much more vulnerable target.
While he can be built as a fighter, Aatrox's stats and kit are similar to those of a melee ADC, like Fiora or Master Yi. These champions are devastating as long as they are able to attack, but are extremely vulnerable to crowd control, and while Aatrox's Blood Well helps him survive, he is no exception to the rule, as a well landed stun or snare can severely hinder his combat abilities.
In particular, not only his damage but his in-lane sustain are dependent on him auto-attacking. Champions with strong blinds like Teemo or Quinn will give him fits during laning.
Inflicting Grievous Wounds can reduce his healing from Blood Thirst.
However, Grievous Wounds does not affect the health he regains from his Aatrox's Blood Well.
Without ability power (which likely won't be built), Massacre's intial damage is not a factor. The large attack speed and range bonus is a huge threat, but you don't have to worry about getting instantly burst-nuked by the activation.
The ability lasts long enough for most teamfights, but baiting Aatrox into using the ability to commit to killing you before a fight breaks out will remove the strong threat the ability presents in a teamfight.
However, it's recommended you only do this if you are a very hard to kill or catch champion, such as Lulu, Zac, Singed, or Karma.
Aatrox is auto attack reliant for not only his damage, but also his survivability. Reducing his attack speed by purchasing Randuin's Omen or Frozen Heart can help reduce both of those components greatly.

http://leagueoflegends.wikia.com/wiki/Aatrox/Strategy