A magical Longsword used by the original Witch Hunters of the Monster Hunters Guild. Utilizing the power of a spell castor against said spell castor as the blade becomes magically sharper when it strikes a creature capable of spell casting (unless the spell casting comes from an item). The abilities of the sword depends on the level of the wielder.

Innate Casting. Witch Hunt blades have a total of 5 charges that recharge after a long rest. These charges can be used to cast the spell Detect Magic and can be used at any level.

Witch Hunt abilities at character's level.
Level 5. Novice Witch Hunter. At this level the wielder can make an attack of opportunity with Witch Hunt against a creature that is casting a spell within their melee attack range. Attacks made with a Witch Hunt weapon also cause a creature to have disadvantage on any checks made to maintain concentration on a spell.

Level 8. Improved Witch Hunter Combat. The sword gives the attuned wielder three superiority dice that are used to make the following maneuvers. 
     Precision Attack. When you make an attack with this weapon against a spell caster, you can expend one superiority die to add it to the attack roll. You can use this ability before or after making the attack roll, but before any of the effects of the attack are applied. 
     Sharpened Attack. When you damage a spell caster with this weapon, you can expend one superiority die to add it to the damage roll. You can use this ability after rolling damage.
     Superior Willpower. When you make an Intelligence, a Wisdom, or a Charisma saving throw, you can expend one superiority die to add it to the roll. You can use this feature only before you learn if the save succeeded or failed.

Level 11. Antimagic Blade. The Witch Hunt gives the attuned the ability to deactivate and even counter magic. When the wielder makes an attack against something magical with the Witch Hunt they can invoke the power of the weapon to cast Dispel Magic. Or if the attuned makes an attack of opportunity with the Witch Hunt against a creature casting a spell they can invoke the blade to cast Counterspell. 
     Both Dispel Magic and Counterspell are cast at their base level (3rd Level) and if the weapon is attempting to counter or dispel magic that requires a higher level the attuned can make a check using either their Intelligence, Wisdom, or Charisma as if they were casting counterspell. The attuned chooses which modifier to use.

Proficiency with a Longsword allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Bonus: Magic, creature that is designated as a Witch Hunter or has the ability to cast Dispel Magic, Counterspell, and or Antimagic Field., Damage, Buff, Debuff, Combat, Versatile, Sap