My PCs have conquered the bad guys in “A Darkness Gathering” and now head off to the North in “Masters of Eternal Night“.  As the PCs open the fleshy sphincter to Crgent’s room he mind blasts them. The monk charges in and the oculus drops from the roof engulfing him.

The original bodyguard was a gelatinous stalker – a bipedal gelatinous cube. But I wanted something more horror themed and “stole” and converted the oculus from Shadow of the Demon Lord.

Medium ooze, unaligned
Armour Class 7
Hit Points 152 (16d8+80)
Speed 20ft.

14 (+2) 3 (-4) 20 (+5) 1 (-5) 6 (-2) 1 (-5)

Damage Immunities lightening
Damage Resistance cold
Condition Immunities blinded, charmed, deafened, exhaustion, frightened, prone
Senses blindsight 120 ft. (blind beyond this radius), passive Perception 12
Languages telepathy 120ft.
Challenge 15 (13,000 XP)

Creep. The oculus moves up to half its Speed as a bonus action. This movement does not trigger free attacks.
Amorphous. An oculus can move freely through openings wide enough to permit the passage of water and can move through spaces occupied by other creatures.
Corrosive Form. A creature that touches the oculus or hits it with a melee attack while within 5 feet of it takes 18 (4d8) acid damage. Any non-magical weapon made of metal or wood that hits the oculus corrodes. After dealing damage, the weapon takes a permanent cumulative -1 penalty to damage rolls. If its penalty drops to -5, the weapon is destroyed. Non-magical ammunition made of metal or wood that hits the oculus is destroyed after dealing damage. The oculus can eat through 2-inch-thick, non-magical wood or metal in 1 round.
Mind-Blasting Horror. A creature looking upon the oculus that is not an aberration must make a DC 15 Sanity saving throw or lose a sanity point. A creature that losses a Sanity point from seeing an oculus is also frightened and is stunned while frightened this way.

Multiattack. The oculus can use its confusion ray then makes three engulfing slam attacks.

Engulfing SlamMelee Weapon Attack: +7 to hit, reach 15 ft., one target.
Hit: 24 (5d6 +5) bludgeoning damage and 10 (3d6) acid damage and the target is grappled (escape DC 17). Until this grapple ends, the target is restrained, and the oculus can’t constrict another target. Constricted targets automatically take 24 (5d6 +5) bludgeoning damage and 21 (6d6) acid damage at the start of the oculus’s turn. The oculus loses one of its engulfing slam attacks while constricting a target.

Confusion RayThe oculus targets one creature that it can sense within 120 feet of it. The target must make a DC 17 Intelligence saving throw or become confused as the spell – the creature can’t take reactions until the start of its next turn and rolls a d8 to determine what it does during its turn. On a 1 to 4, the creature does nothing. On a 5 or 6, the creature takes no action or bonus action and uses all its movement to move in a randomly determined direction. On a 7 or 8, the creature makes a melee attack against a randomly determined creature within its reach or does nothing if it can’t make such an attack.

Muddle.When the gelatinous stalker is hit it may use its reaction to attack with confusion ray against the triggering creature.

A quivering red eye drifts across a slick of greenish-yellow slime, reeking of sickness and disease. Visible in its membranous body are floating scraps of skin and pieces of bone. Oculi bubble into the world through mirrors warped by the Far Realm’s influence.
Dimly sentient, they can be commanded by intelligent aberrations, otherwise they relentlessly search for flesh to eat. When one discovers something edible, it flows over the prey to dissolve the meat and bones with its corrosive secretions. Its horrific appearance can pin potential prey in place, greatly easing the process.