Poison Blade

The Poison Blade is a Hidden Needle with a poison, and whoever you injected with the poison will go berserk, swinging their weapon wildly and attacking all those in range, but not killing them unless they're already low on health or are hit multiple consecutive times. Ezio can "recharge" his weapon by buying poison from doctors.

Poison vials cost 250 florins each and you can carry up to five vials, but poison pouch upgrades bought from the Tailor raise the amount of vials you can carry at once.