Metabot's Manual of Magical Maneuvers

Sinister Blade

3-level Enchantment

As a reaction to a hostile creature coming into range, or a creature in range becoming hostile, you unsheathe part of your blade. You imbue this simple implication with a magically binding threat. That creature can choose to end its turn immediately and be charmed by you until the spell ends or until you or your companions do something harmful to it or its allies.
If it isn't charmed, it must make a Wisdom saving throw. On a failed save, the creature is frightened of you and you have advantage on melee attack rolls against it. At the end of each of its turns, the target can make another Wisdom saving throw. On a success, the spell ends on the target.
At higher levels: When you cast this spell using a spell slot of 5th level or higher, the spell does not require concentration.