Devil's Sight. Magical darkness doesn't impede the devil's darkvision.

Magic Resistance. The devil has advantage on saving throws against spells and other magical effects.

Spellcasting. The Middle manager is a 4th -level spellcaster. Its spellcasting ability is intelligence (spell save DC 15, +7 to hit with spell attacks). The Middle manager  has following [Wizard] spells prepared:
Cantrips (at will): [Acid splash], [Mending] 
1st level (4 slots): [Acid Stream], [Chromatic Orb], [Charm Person] 

2nd Level (3 Slots) [Melf's Acid Arrow], [Crown of Madness] 

Scepter. Melee Weapon Attack: +4 to hit, reach 5 ft., 1 target. Hit: 3 (1d6 + 1) bludgeoning damage. 

Corrosive Enchantment. The manager can touch one ally to add 5 acid damage to their melee attacks until the end of their turn. This deals 2 acid damage to the ally. 

Paid Off. One creature within 10 feet of the manager must make a CHA saving throw (DC 15). If they fail the devil can move the creature up to 15 ft and the creature makes a melee basic attack as a free action against a creature of the devil's choice. If a target’s saving throw is successful, or if the effect ends for it, the creature is immune to Paid Off for the next 24hrs.

Corrosive Dispersion. The manager can dissolve into a pool of corrosive metal and move 20 ft in any direction. If the manager moves through a square occupied by any other creature it must make a Dex check or take 7 (1d6+5) acid damage (save negates). It can't end its turn in an occupied space or in a solid object. 3/Day

Infernal Performance Review. When an ally the manager can see misses with an Attack roll or fails a skill check, they may cause the ally to take 2 points of psychic damage to re-roll the attack  roll or skill check with a bonus equal to half the charisma modifier of the manager (2) 

Corrosive Blood. Whenever the middle manager takes damage from a melee range attack, its attacker must make a Dex saving throw (dc 12) or take 2 (1d6) acid damage from the corrosive metal that runs in this devil's veins.