Ahh Gerrzog, the original adventure was designed for 1st level characters so something like a glaberzu would be impossible for the group to take on so they would be forced to figure out a different way. But I knew my PCs who are level 15 would charge in, and charge in they did.
I didn’t change the CR of Gerrzog from the original 5e MM version. I did add some extra abilities but nothing crazy. The key advantage was terrain along with four initiative counts. That combined with the fact the party effectively had no magic items and the sorceress had to roll on the wild magic table each time she cast a spell made for a much more interesting fight.
I also had an unstable 170 foot bridge of twisted stair-rails they had to traverse across to get to him. Gerrzog confronted the party when they were half-way across since they made no pretence of being sneaky, and would bounce his 6,000 lbs bulk on the bridge as one of his move actions making everyone on the bridge DC 15 dexterity checks or fall to the platform 120 feet below.
Tufast the cleric fell during the first round and he never made it back up in time. Sylvanus the monk was knocked out on the first attack (she only had 35 hit points to begin with). In the end Heidt the Mechromancer killed Gerrzog when he was caught in the fiends grapple. He unloaded his lasgun on full auto into the fiends face. The last thing Gerrzog said before being banished back to the abyss was – “I’ll remember you” to Heidt.
Good fight 🙂
Large fiend (tanar’ri), chaotic evil
Armour Class 19 (natural armour)
Hit Points 225 (15d10 +75) (112)
Speed 40 ft.
STR 20 (+5) DEX 16 (+3) CON 21 (+5)
INT 19 (+4) WIS 17 (+3) CHA 16 (+3)
Saving Throws Str +9, Con +9, Wis +7, Cha +7
Damage Resistances cold, fire, lightning; bludgeoning, piercing, and slashing from non magical weapons
Damage Immunities poison
Condition Immunities poisoned
Senses truesight 120ft., passive Perception 13
Languages Abyssal, telepathy 120ft.
Challenge 9 (5,000 XP)
Brute. Gerrzog is a brute and all melee attacks he makes gain one extra die of damage (included).
Chaos’ Sight. Magical darkness doesn’t impede Gerrzog’s darkvision .
Innate Spellcasting. Gerrzog’s spellcasting ability is Intelligence (spell save DC 16). The glabrezu can innately cast the following spells, requiring no material components:
At will: darkness (15 ft, moves with target), detect magic (always active), and dispel magic
1/day each: confusion (WIS), fly, power word stun (<150 hp, CON at end), and charm person
1/week: plane shift
Magic Resistance. The glabrezu has advantage on saving throws against spells and other magical effects.
Arcane Fury. When first reduced to half hit-points (bloodied state) Gerzog teleports up to 100 feet, recharges all his used spells, and makes an abyssal bolt attack against all hostile targets within range.
Multiattack. The glabrezu makes four attacks: two with its pincers and two with its fists or four abyssal bolt. Gerzog can also cast one spell or summon more demons.
Pincer. Melee Weapon Attack: +9 to hit, reach 10ft., one target.
Hit: 20 (3d10 + 5) piercing damage. If the target is a Medium or smaller creature, it is grappled (escape DC 15). The glabrezu has two pincers, each of which can grapple only one target. Grappled creatures automatically suffer 16 (2d10 + 5) bludgeoning damage at the start of Gerrzog’s turn.
Fist. Melee Weapon Attack: +9 to hit, reach 5 ft., one target.
Hit: 13 (3d4 + 5) bludgeoning damage. On a critical hit the target must make a DC 15 Constitution save or be stunned for 1 minute. The stunned creature can make a save at the start of its turn to clear the status affect.
Abyssal Bolt. Ranged Spell Attack: +9 to hit, reach 120ft., one target.
Hit: 13 (3d4 + 7) fire damage.
Summon Demons (1/Day). Gerzog attempts to summon more of its kind. The Gerzog only has a 30% chance of success and may call 1d3 vrocks, 1d2 hezrous, or one glabrezu. However due to various machinations and favours garnered through centuries of deception and deal making Gerzog may always summon 1d8 manes who remain in his service permnantly. Or he may summon two named chasme with 100% chance as well. He usually uses the chasme to carry him about when he has consumed his fly spell.
The summoned demons appears in an unoccupied space within 60 feet of its Gerzog, acts as an ally of Gerzog, and can’t summon other demons. It remains for 10 minutes, until it or its Gerzog dies, or until Gerzog dismisses it as an action.
Four arms grace the torso of this towering monstrosity. The monster’s eyes shine with a mix of intelligence and cruelty. A glabrezu stands 18 feet tall and weighs just over 6,000 pounds. These treacherous demons form from the souls of the treasonous, the false, and the subversive—souls of mortals who, in life, bore false witness or used treachery and deceit to ruin the lives of others.