The assassin's blade is a bracer that one can wear on their arm and underneath is a extendable blade that can be extended on a action for combat or when you hold your action and extend the blade and as a bouns action you can retract the blade also it gives you sneak attack if your not holding a weapon.
Proficiency with a Dagger allows you to add your proficiency bonus to the attack roll for any attack you make with it.
This weapon has the following mastery property. To use this property, you must have a feature that lets you use it.
Nick. When you make the extra attack of the Light property, you can make it as part of the Attack action instead of as a Bonus Action. You can make this extra attack only once per turn.
Notes: Damage: Piercing, cannot be thrown, rouge, Finesse, Light, Thrown, Nick