Rapier Master (5e Feat)
From D&D Wiki
You have mastered the art of wielding a rapier to pierce your target's defenses and parry opponent's attacks. You gain the following benefits when using a rapier:
- You gain a +1 bonus to attack rolls you make with a rapier.
- As a bonus action, you can search your opponent for vulnerabilities. Choose a creature you can see within 5 feet of you. Before the start of your next turn, your next attack that hits the creature with a rapier deals an extra 1d4 piercing damage on a hit.
- As a bonus action, you can prepare to pierce your target's defenses. Choose a creature you can see within 5 feet of you. Before the end of your next turn, the next time you would make an attack with a rapier against the creature, instead, the creature must make a Dexterity saving throw (DC 8 + your Dexterity modifier + your proficiency bonus, if you are proficient with rapiers). If the replaced attack roll would have had advantage, the target makes the dexterity saving throw with disadvantage. On a failed save the target takes the attack’s normal damage and suffers any additional effects.