Battle flare

The Battle flares were explosive viols of liquid created by Leonardo da Vinci as a new form of munition against Milan. Dropping them at night would cause a small explosion, letting out a huge flash, temporarily blinding the enemy.

History
Leo showed the other apprentices the battle flare when he realized the rack of flares had been taken from the table and used by Verrocchio as foreground for his painting. When Leo took them back, Verrocchio angrily moved the table, accidentally knocking one of the flares to the floor, causing a small explosion. Leonardo later used a battle flare to save Tomaso Gherardini from Silvio Pirelli. The effect of the flare distracted him enough for her to beat him and win their dual. (By the Sword)