Source: Critical Role

Weapon (dagger), ??? (requires attunement)

This silver stiletto blade bears intricate grooves that spiral from the point to the ivory hilt and handle. You have a +2 bonus to attack and damage rolls made with this weapon. While attuned to this dagger, you can spend an action to place the point of the blade into any keyhole and seal it shut. A keyhole sealed in this way cannot be unlocked until this dagger is placed into that keyhole once more. Attempting to seal a keyhole unseals any previous sealed keyholes.

The blade itself looks almost like Damascus steel, with spiraling grooves. It appears more like a stiletto, as opposed to like a bladed dagger.