Mailbreaker

Mailbreaker is a type of dagger used by the assassins that are members of the Eight Fingers organization.

Description
Mailbreaker is a weapon originating from the New World. They are used by Eight Fingers' assassins to silently kill off Sebas Tian without the latter noticing their presence from behind him.

Appearance
Brain Unglaus noted that these weapons look like a double-edge sword in the shape of a dagger.

Abilities
There were reservoirs carved into the blades of this weapon and said reservoirs reflected the oily glow of a dangerous liquid. Mailbreakers were weapons specialized for thrusting attacks. It is also the kind of ranged weapons thrown at their specific target from afar.

Trivia

 * In the real world, it is a parrying dagger a type of small handheld weapon from the European late Middle Ages and early Renaissance.