Duergar Resilience. The duergar has advantage on saving throws against poison, spells, and illusions, as well as to resist being charmed or paralyzed.

Sunlight Sensitivity. While in sunlight, the duergar has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Combat Inspiration (4 / Times, d8). A creature that has a Bardic Inspiration die from you can roll that die and add the number rolled to a weapon damage roll it just made. Alternatively, when an attack roll is made against the creature, it can use its reaction to roll the Bardic Inspiration die and add the number rolled to its AC against that attack, after seeing the roll but before knowing whether it hits or misses.

Spellcasting. Bendahild Branma is a 7th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 16, +8 to hit with spell attacks). Bendahild Branma has the following Bard spells:

Cantrips (at will): Vicious Mockery, Message, Prestidigitation, Minor Illusion, Booming Blade

1st level (4 slots): Bless(C), Charm Person(C),Dissonant Whispers, Earth Tremor, Tasha's Hideous Laughter(C)

2nd level (3 slots): Hold Person(C), Shatter

3rd level (3 slots): Dispel Magic, Fear(C), Counterspell

4th level (1 slots): Dimension Door

Magic Resistance. Bendahild has advantage on all saving throws against magical effects.

Equipment. Cloak of Displacement (A), Boots of Elvenkind

Enlarge (Recharges after a Short or Long Rest). For 1 minute, the duergar magically increases in size, along with anything it is wearing or carrying. While enlarged, the duergar is Large, doubles its damage dice on Strength-based weapon attacks (included in the attacks), and makes Strength checks and Strength saving throws with advantage. If the duergar lacks the room to become Large, it attains the maximum size possible in the space available.

Dancing Sword (Rapier). Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 9 (1d8 + 5) piercing damage, or 14 (2d8 + 5) piercing damage while enlarged.

Invisibility (Recharges after a Short or Long Rest). The duergar magically turns invisible until it attacks, casts a spell, or uses its Enlarge, or until its concentration is broken, up to 1 hour (as if concentrating on a spell). Any equipment the duergar wears or carries is invisible with it.

Cutting Words. When a creature that you can see within 60 feet of you makes an attack roll, an ability check, or a damage roll,  Expend one of your uses of Bardic Inspiration, rolling a Bardic Inspiration die and subtracting the number rolled from the creature’s roll. You can choose to use this feature after the creature makes its roll, but before the DM determines whether the attack roll or ability check succeeds or fails, or before the creature deals its damage. The creature is immune if it can’t hear you or if it’s immune to being charmed.