Stalker

Stalker is a one of the Five Blades of Corusk. It is a longsword with a blue steel blade and a hilt, pommel, and crosspiece of black adamantine. Wisps of shadowstuff seem to move silently across its surface. When you are not attuned to it, you gain a +1 bonus to your attack and damage rolls made with this magic weapon. When you are attuned to it, you gain a +3 bonus to your attack and damage rolls made with this magic weapon, and you gain advantage on any Dexterity (Stealth) and Wisdom (Survival) check.

Sap (Mastery): If you hit a creature with this weapon, that creature has Disadvantage on its next attack roll before the start of your next turn.

Versatile: A Versatile weapon can be used with one or two hands. A damage value in parentheses appears with the property. The weapon deals that damage when used with two hands to make a melee attack.

Proficiency: martial, longsword Source: Treasures from Oerth p. 41 (Homebrew), Player's Handbook (2024) p. 215