Constrictor. The Face of Illurthane has advantage to grapple and to resist its grapple being broken. Overly Keen Senses. Once per turn sensing horrid smells and tastes will cause the Face of Illurthane to use its reaction to gag, and it makes a DC14 Constitution saving throw to avoid vomiting up all creatures it swallowed. 360-Degree Vision. The Face of Illurthane can't be flanked.
Multiattack. The Face of Illurthane may use its Constrict ability, then it makes two attacks in any combination.
Acidic Blister. Ranged Weapon Attack: +8, Range 25/100, a 5-foot-radius sphere. Hit: 2d6 acid damage.
Probe. Melee Weapon Attack: +9, Reach 20 ft., one target. Hit: 3d6 psychic damage.
Swipe. Melee Weapon Attack: +9, Reach 15 ft., one target. Hit: 1d10+6 slashing damage.
Constrict. The Face of Illurthane attempts to restrain any creature within its melee range or its space. It makes an opposed Athletics check against the target. If the target fails, it is Restrained until it uses its action to make another opposed Athletics check. At the beginning of the target's turn, if it's grappled, it takes 2d6 bludgeoning and 1d6 acid damage. The Face of Illurthane can grapple up to three creatures in this way.
The Face of Illurthane is a strange aberration that appears akin to a humanoid manta ray or hooded snake. Mostly blind, the Face of Illurthane has highly-attuned senses of smell and touch. It silently stalks the Mountains of Illurthane, searching for humanoid prey and only for humanoid prey.