Grist

Ghoul Fever: Any creature which takes damage from a grist's bite or claw attack must, after a day has passed, succeed in a DC 12 Constitution save or become infected with ghoul fever and suffer 2d10 necrotic damage. While infected the creature cannot be healed by non-magical means. Each day thereafter the creature must make another Constitution save or take an additional 2d10 necrotic damage. Once contracted ghoul fever may only be cured by magical means such as cure disease. 

An afflicted humanoid that dies while infected with ghoul fever rises as a ghoul (the lesser version found in the MM) at the next midnight. A humanoid who becomes a ghoul in this way retains none of the abilities it possessed in life. It is not under the control of any other ghouls, but it hungers for the flesh of the living and behaves like a normal ghoul in all respects. A humanoid of 4 Hit Dice or more rises as a ghast, not a ghoul.

Shadow resistance: While in dim light or darkness, the grist has resistance to all damage. 

Stench: The stink of death and corruption surrounding these creatures is overwhelming. Living creatures within 10 feet must succeed on a DC 12 Constitution save or be poised until the start of its next turn. A creature that successfully saves cannot be affected again by the same grist’s stench for 24 hours.

Turning Defiance: The grist and any ghasts or ghouls within 30 feet of it have advantage on saving throws against effects that turn undead. 

Multiattack. The grist makes two attacks. One with its bite and one with its claws. 

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 13 (2d8 + 4) piercing damage.
Claws. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage. If the target is a creature other than an elf or undead, it must succeed on a DC 12 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.