Bonepowder Ghoul

The bonepowder ghoul can move through a space as narrow as 1 inch wide without squeezing.

Whenever a bonepowder ghoul drains life force from victims with Gravedust, it can use that energy transform its shape into a more solid form and maintain it. The new form is Small and semi-transparent but roughly the shape of a normal ghoul. In this form, the ghoul isn't amorphous and can't form a whirlwind, but it can speak normally and manipulate objects. The altered form lasts for 1 minute for every point of necrotic damage it delivered against living foes.

the bonepowder ghoul's innate spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). It can innately cast the following spells, requiring no material components:

at will: chill touch, darkness, dispel magic, ray of enfeeblement

3/day: blindness/deafness, circle of death (7th level; 10d6)

1/day: finger of death

The bonepowder ghoul and any other ghouls within 30 feet of it have advantage on saving throws against effects that turn undead.

Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 18 (3d8 + 5) plus 1d4 Strength damage, and the target must succeed on a DC 17 Constitution saving throw or be paralyzed for 1d4 + 1 rounds. If the target creature is humanoid, it must succeed on a second DC 19 Constitution saving throw or contract darakhul fever.

A bonepowder ghoul can project a 40-ft. cone of grave dust. All targets within the area must make a DC 19 Dexterity saving throw to avoid taking 4d8 necrotic damage, and must make a second DC 17 Constitution saving throw to avoid being infected with darakhul fever.

A bonepowder ghoul can generate a whirlwind of bones and teeth. All creatures within a 20-foot cube take 66 (12d10) slashing damage and are drained of 1d6 Strength; a successful DC 17 Dexterity saving throw reduces damage to half and negates the Strength loss. The whirlwind dissipates after one round.