Whenever Aatrox consumes health, he stores it into his Blood Well, which can hold up to 105 - 870 (based on level) health. The Blood Well depletes by 2% per second if Aatrox hasn't dealt or received damage in the last 5 seconds.
Aatrox gains 0.3 - 0.55 (based on level)% bonus attack speed for every 1% in his Blood Well, up to a maximum of 30 - 55 (based on level)% bonus attack speed.
Upon taking fatal damage, Aatrox is cleansed of all debuffs, enters stasis and drains his Blood Well, healing himself over the next 3 seconds for 36.75 - 304.5 (based on level) health(+ 100% of Blood Well's stored health) up to a maximum of 141.75 - 1174.5 (based on level) health.
When Aatrox enters stasis while he was being targeted by a turret, the turret will choose a new priority target and Aatrox will not be targeted even after stasis ends (unless he or an allied champion is the only viable target for the turret). In other words, Aatrox will drop turret aggro when he enters stasis.
The attack counter between Blood Thirst and Blood Price is shared, meaning that toggling the ability with one empowered attack prepared will immediately allow use of the empowered attack of the other.
Toggling between Blood Thirst and Blood Price does not reset the basic attack timer. It will, however, cancel an empowered basic attack in its windup animation if it is toggled during that time.
Toggled abilities do not count as ability activation for the purposes of effects such as Spellblade or Force Pulse.
Aatrox's basic attack animation correlates with the amount of stacks for Blood Thirst/Price. The first basic attack animation (after leveling up Blood Thirst/Price or proccing an empowered basic attack) is Aatrox swinging his sword to the left, the second is to the right and the third basic attack animation (which will be affected by Blood Thirst/Price) is Aatrox stabbing the target.