Chain-ghast

Stench. Any creature that starts its turn within 5 feet of the ghast must succeed on a DC 10 Constitution saving throw or be poisoned until the start of its next turn. On a successful saving throw, the creature is immune to the ghast's Stench for 24 hours.

Chains of captivity. Any creature that starts its turn on flat ground within 5 feet of Chain-ghast must make a athletics saving throw. If they fail, they are restrained. This condition can only be removed with a Ghastly Key.

Bite. Melee Weapon Attack: +3 to hit, reach 5 ft., one creature. Hit: 12 (2d8 + 3) piercing damage.

Claws. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) slashing damage. If the target is a creature other than an undead, it must succeed on a DC 10 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.

Chain Whip Melee Weapon Attack +7 to hit, reach 15 ft., one creature. Hit: 23 3d12+1

If an enemy sets foot within a cell that is within 10 feet of a Chain-Ghast, the chain-ghast will use his next action to move over to the cell and lock it.