Plague Mask. The doctor can breathe normally in any environment, and has advantage on saving throws made against harmful gases and vapors (such as [Tooltip Not Found] effects and inhaled poisons). The doctors vision isn't obscured while inside gases and vapors. 

Spellcasting. The doctor is a 5th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 13, +5 to hit with spell attacks). The doctor has the following wizard spells prepared:

Cantrips (at will): acid splash, mage hand, poison spray, acid splash, prestidigitation

1st level (4 slots): detect magic, mage armor, shield

2nd level (3 slots): acid arrow, suggestion

3rd level (2 slots): counterspell, stinking cloud

Scythe. Melee Weapon Attack: +5 to hit, reach 10 ft., one target. Hit: 5 (1d4 + 3) slashing damage, or 11 (2d4 + 3) slashing damage if two-handed.

Acid Vial. Ranged Weapon Attack: +5 to hit, range 20 ft., one target. Hit: 7 (2d6) acid damage.

Poison Vial. The doctor lobs a vial of poisonous gas at a target area that it can see within 30 feet, when the vial breaks the gas spreads out in a 10-foot radius sphere. Creatures caught in the gas must succeed on a DC 13 Constitution saving throw or take 13 (3d8) poison damage and become poisoned for 1 hour. 

Sleeping Vial. The doctor lobs a vial of sleeping gas at a target area that it can see within 30 feet, when the vial breaks the gas spreads out in a 10-foot radius sphere. Creatures caught in the gas must succeed on a DC 13 Constitution saving throw or fall unconscious for 1 minute. A creature can shake an unconscious creature awake if they are within 5-feet of it and with an action.