BhaalSpawn

Cunning Action. On each of its turns, the spy can use a bonus action to take the Dash, Disengage, or Hide action.

Pickpocket.  The Halfling thief gains an additional +4 to Sleight of Hand while attempting to steal either currency or unenchanted weapons.  Furthermore, the thief will gain an additional +1 if there is another Halfling Thief within 10ft.

Sneak Attack (1/Turn). The spy deals an extra 7 (2d6) damage when it hits a target with a weapon attack and has advantage on the attack roll, or when the target is within 5 feet of an ally of the spy that isn't incapacitated and the spy doesn't have disadvantage on the attack roll.

Evasion: If the Bhaalspawn is subjugated to an effect that allows it to make a Dexterity saving throw to take only half damage, the Bhaalspawn instead takes no damage if it succeeds on the saving throw, and only half damage if it fails.

Multiattack. The spy makes two melee attacks.

Spear. Melee or Ranged Weapon Attack: +3 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 4 (1d6 + 1) piercing damage, or 5 (1d8 + 1) piercing damage if used with two hands to make a melee attack.

Dagger. Melee or Ranged Weapon Attack: +6 to hit, reach 5 ft or range 20/60 ft., one target. Hit: 5 (1d4 + 3) piercing damage, and the target must make a DC 15 Constitution saving throw, taking 18 (4d6) necrotic damage on a failed save, or half as much damage on a successful one. 

Shortsword. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) piercing damage.

Hand Crossbow. Ranged Weapon Attack: +4 to hit, range 30/120 ft., one target. Hit: 5 (1d6 + 2) piercing damage.

spell scrolls

Spell Scrolls of Blur x3  - Concentration, any creature has Disadvantage on attack rolls against you.

Spell Scrolls of Darkness x3

Concentration: - 60 feet - For the duration, magical darkness spreads from a point within range and fills a 15-foot-radius Sphere.

Spell Scrolls of Heat Metal x3 

Concentration: - 60 feet - Any creature in physical contact with the object takes 2d8 Fire damage when you cast the spell. Until the spell ends, you can take a bonus action on each of your later turns to deal this damage again if the object is within range.

If a creature is holding or wearing the object and takes the damage from it, the creature must succeed on a Constitution saving throw or drop the object if it can. If it doesn't drop the object, it has disadvantage on attack rolls and ability checks until the start of your next turn.

Spell Scrolls of Hold Person x5

Concentration: - Range: 60 feet - Choose a Humanoid that you can see within range. The target must succeed on a Wisdom saving throw or have the paralyzed condition for the duration. At the end of each of its turns, the target repeats the save, ending the spell on itself on a success.

Spell Scrolls of Invisibility x3 

Concentration: - Range: Touch - The spell ends early immediately after the target makes an attack roll, deals damage, or casts a spell.

Spell Scrolls of Knock x3

Spell Scrolls of Mirror Image x2

Range: Touch- (3 Duplicates) If Hit, roll a d6 for each of your remaining duplicates. If any of the d6s rolls a 3 or higher, one of the duplicates is hit instead of you.

Spell Scrolls of Silence x2

Concentration: - Range: 120 feet: 20-foot-radius Sphere centered on a point you choose within range. Any creature or object entirely inside the Sphere has immune to Thunder damage, and creatures have the defend condition while entirely inside it. Casting a spell that includes a Verbal component is impossible there.

Uncanny Dodge. The Bhaalspawn halves the damage that it takes from an attack that hits it. The thief must be able to see the attacker.

Transformation:  The Slayer, Avatar of Bahaal 

At 50% HP the Bhaal Spawn transforms into The Slayer.