Narcellia's Headband of Intellect. Bad Fruul has an Intelligence score is 19 while it wears this headband. It can also speak telepathically with a drow priestess of Lolth named Narcellia Varam’myr, whose soul is trapped within the headband.

Hill Rune. Bad Fruul has a hill rune inscribed on his chest, letting it use its Stone Avalanche action and Hill Rebuff reaction.

Stone Rune. Bad Fruul has a stone rune inscribed on a sceptre in its possession. While holding the sceptre bearing the rune, Bad Fruul can use its Prismatic Rays action.

Frost Rune. Bad Fruul has a frost rune inscribed on a shield in its possession. While holding shield bearing the rune, Bad Fruul can use its Ice Armor reaction.

Blood Rune. Bad Fruul has a blood rune inscribed on a belt in its possession. While wearing the belt bearing the rune, Bad Fruul can use its Corrupting Hex bonus action.

Each object bearing a rune has AC 16; 30 hit points; and immunity to necrotic, poison, and psychic damage. The object regains all its hit points at the end of every turn, but it turns to dust if reduced to 0 hit points or when Bad Fruul dies. If the rune is destroyed, Bad Fruul can inscribe each rune on an object in its possession when it finishes a short or long rest.

Legendary Resistance (3/Day). If Bad Fruul fails a saving throw, it can choose to succeed instead.

Multiattack. Bad Fruul makes one Prism Sceptre attack and uses Stone Bolas.

Prism Sceptre. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 18 (3d8 + 5) bludgeoning damage plus 9 (2d8) thunder damage.

Stone Bolas. Bad Fruul conjures three stone balls connected by lines of magical force and throws them at one creature it can see within 60 feet of itself. The target must make a DC 17 Dexterity saving throw. On a failed save, the target has the restrained condition until the start of Bad Fruul’s next turn, and the stones erupt in a burst of thunderous energy that deals 14 (4d6) thunder damage to the target and each creature within 10 feet of the target. On a successful save, the stones vanish without erupting.

Stone Avalanche (Requires Hill Rune). Bad Fruul conjures a hail of rocks in a 20-foot-radius, 40-foot-high cylinder centered on a point on the ground it can see within 120 feet of itself. Each creature in that area must make a DC 17 Dexterity saving throw. On a failed save, a creature takes 28 (8d6) bludgeoning damage and has the prone condition. On a successful save, a creature takes half as much damage only.

The rocks turn the ground in that area into difficult terrain.

Prismatic Rays (Requires Stone Rune). Bad Fruul’s stone rune emits beams of light that form a 60-foot cone. Each creature in that area must make a DC 17 Dexterity saving throw. For each creature in that area, roll a d6 to determine what ray affects it:

1–2: Blazing Red. On a failed save, the creature takes 35 (10d6) radiant damage and has the blinded condition until the end of Bad Fruul’s next turn. On a successful save, the creature takes half as much damage only.

3–4: Dreadful Blue. On a failed save, the creature takes 35 (10d6) necrotic damage and has the frightened condition until the end of Bad Fruul’s next turn. On a successful save, the creature takes half as much damage only.

5–6: Sapping Green. On a failed save, the creature takes 35 (10d6) force damage and has the incapacitated condition until the end of Bad Fruul’s next turn. On a successful save, the creature takes half as much damage only.

Corrupting Hex (Requires Blood Rune). Bad Fruul targets one creature it can see within 60 feet of itself. The target must succeed on a DC 17 Charisma saving throw or take 13 (3d8) necrotic damage and become cursed for 24 hours. While cursed this way, the target’s speed is reduced by half, and if it tries to cast a spell, it must first succeed on a DC 17 Intelligence check or the spell fails and is wasted.

Hill Rebuff (Requires Hill Rune). Immediately after Bad Fruul takes damage from a creature it can see within 10 feet of itself, that creature must succeed on a DC 17 Constitution saving throw or take 10 (3d6) force damage and be pushed horizontally 10 feet away from Bad Fruul.

Ice Armor (Requires Frost Rune). When a creature Bad Fruul can see makes an attack roll against it, Bad Fruul can form a coat of ice around itself, granting it a +5 bonus to its AC against that attack. After the attack hits or misses, the ice shatters, and each creature within 5 feet of Bad Fruul must succeed on a DC 17 Dexterity saving throw or take 13 (3d8) cold damage.