Poison Blade

"It's another blade design...for delivering poison!"

- Leonardo da Vinci

The Poison Blade is one of the several expansions of the Hidden Blade invented by Altaïr ibn-La'Ahad while using the Apple of Eden, later crafted by Leonardo da Vinci for use by Ezio Auditore, essentially being a thin, hollow needle hidden within the blade that can be filled with poison. The blade can be used to inconspicuously inject the target with said poison, causing the target to attack anyone a several foot radius with whatever weapon they have on hand, and then suddenly die, all within a time frame of under thirty seconds. Ezio can replenish his supply of poison by buying poison vials from Doctors.

This is one of the best stealth weapons the player will acquire within the entire game, as it allows Ezio to silently assassinate someone without attracting any attention to himself. Besides dealing a direct kill to the intended assassination target, the Poison Blade can also be used as a cover for one, as anyone within the immediate area will stop to watch the poisoned victim, creating a stealth assassination opportunity if one of the spectators happens to be a target, since all other eyes will be on the poisoned victim. Additionally, one can poison someone as a distraction to cover an approach to a restricted area, since you can slip by while the guards watch the person you just previously poisoned. The Poison Blade is especially useful when completing Assassination Contracts, as in many cases targets will either be followed by guards or be in a guarded area.

Poison vials can be bought from a Doctor at 175 florins each and up to five can be carried with the small poison vial provided, but this can be upgraded to ten or fifteen with the medium and large poison vials, purchasable from any Tailor.

Assassin's Creed: Brotherhood
Assassin's Creed: Brotherhood introduces fast poison, which can be purchased from doctors. Fast poison makes enemies go directly into berserk mode. This is a more precise way to create a diversion, because you don’t have to wait a few seconds before the poisoned NPC starts slashing wildly around him. Also, you are now given the option to buy the poison darts upgrade for your Hidden Gun from Leonardo that lets you poison enemies from a ranged distance with high precision.

Ways to use the Poison Blade efficiently:
The Poison Blade is the most discrete weapon in the game, and as such, has multiple uses that all pertain to stealth assassinations:
 * 1) Silent Kill - Guards will not notice the poisoning process, unless it is directly next to them and in their line of sight; though sometimes, even then, they will not notice.
 * 2) Attention - Distraction is an important tool to use during missions. If you are looking for a silent approach that smoke bombs cannot provide, and cannot find thieves, mercenaries, or courtesans within the immediate area, the Poison Blade can be used as an effective substitute. Poisoning anyone within ten meters of a guard's position will cause him, as well as all other guards near him, to move away from their position to where the poisoned victim is standing. Once the victim has drawn their attention, the player has can either assassinate the guards and give away their position, or silently head on to their objective. It is important to leave the area before the poisoned victim has died, as the guards with start an investigation afterward, and become suspicious of the player if they are in the guards' line of sight.
 * 3) Clean Kill - When performing an Assassination Contract, a single target may have at least one guard following close behind them. One can poison the guard and move away into hiding, while the aforementioned guard may inadvertently kill the target for you, eliminating the need to ever come out of hiding after the first poisoning.

Trivia

 * The "doctor" achievement/trophy can be earned by performing an air assassination on an already poisoned guard.
 * If you poison two guards who are close to each other, one may knock the other one out. In this case the knocked out guard will not die, though he has been poisoned, but remain knocked out as if he was beaten in a fistfight.