Need stat help for a creature equivalent to two spined devils

[1Forge]

I know it's kinda specific but I lack a monster Manuel and I need to have an encounter ready for tomorrow.
The party has been split up by a city of possessed teiflings, they will have to find a way to cure them (using holy water) theyll have to fight commoner stat possessed teiflings, "taken" teiflings with demon bonuses and the demon king (the possesed ruler of a city state composed only of teiflings. With the help of Ninja_Prawn the taken teiflings were given stats and they calculated the encounter difficulty. the setup i want to use would be to difficult if i kept the demon king, but he is so important to the story I need him to stay. Basically i need to replace the encounters spined devils with the possessed king to maintain balence. But because I don't have a MM I have no idea how powerful spined devils are, I've drawn up an idea for the boss but I'm not sure that it is balanced.

HP:unknown
AC:
STR DEX CON INT WIS CHA
14 16 18 19 12 14
immunities: necrotic, force, fire, psychic
resistances: piercing, slashing, bludgeoning from non magical weapons.
status immunities: Charmed
attacks: The Taken King has 2 attacks per turn and can sacrifice any attack to cast a spell instead.

Abyssal runes: every turn a walls of fire eminate from him in all directions randomly all creatures must make a DC:10 dexterity save each turn they are within 30 ft of him(stats of agnazzars scorcher)

Claws of R'tae: The kings hands have been transfigured by R'taes magics causing 1d6 necrotic damage to any living thing touched by them.

Arcane Hunger: The king can attempt to devour the magic from any item or person within 5 ft if the target is a non divine spellcaster they must make a will save DC:15 on a failed save they apply the effect of anti magic feild on themselves for 1d4 turns, on a sucess the king has disadvantage on his next action. Non spellcasters are immune and may take an opportunity attack.

anyway gtg please help me balance this concept to a working boss! Thank you!

[Ninja_Prawn]

Sounds like a perfect opportunity to use Angry's paragon monster rules.

I'll see if I can put something together this morning.

[Ninja_Prawn]

The Taken King
Medium fiend (devil), lawful evil
Armour Class 13
Hit Points 34/34 (4D8 + 16 ea.)
Speed Humanoid form: 30 ft.; Devil form: 20 ft., fly 40 ft.


STR
DEX
CON
INT
WIS
CHA


14 (+2)
16 (+3)
18 (+4)
19 (+4)
12 (+1)
14 (+2)


Damage Resistances bludgeoning, piercing and slashing from nonmagical weapons
Damage Immunities fire, force, necrotic, psychic
Condition Immunities charmed
Senses blindsight 60ft., darkvision 120ft., passive Perception 11
Languages Common, Infernal, Telepathy 120ft.
Challenge Paragon 2 (900 XP) - counts as two creatures.

Magic Resistance. The Taken King has advantage on saving throws against spells and other magical effects.

Devil's Sight. Magical darkness does not impede the Taken King's darkvision.

Limited Spines. When in Devil form, the Taken King has 12 tail spines, which function as ammunition for his Tail Spine attack. The spines regrow after the Taken King completes a long rest.

Claws of R'tae (Humanoid form only). The Taken King's weapon attacks are magical and deal an extra 3 (1d6) necrotic damage on a hit.

Flyby (Devil form only). The Taken King doesn't provoke an opportunity attack when he flies out of an enemy's reach.

Actions
Multiattack (Humanoid form). The Taken King uses his Arcane Hunger ability and then makes one attack with his Claws, or he makes two attacks with his Claws.

Multiattack (Devil form). The Taken King makes two attacks: two with his Claws or two with his Tail Spines.

Claw. Melee Weapon Attack: +4 to hit, reach 5ft., one target. Hit: 5 (1d6 + 2) slashing damage.

Searing Rune (Recharge 5-6). The area around the Taken King erupts with swirling patterns of flame, tracing out a blasphemous rune. Each creature within 30 feet of the Taken King takes 10 (3d6) fire damage or half as much if it succeeds on a DC 14 Dexterity saving throw.

Arcane Hunger (Humanoid form only). The Taken King chooses one creature, object or magical effect he can see within 120 feet. All spells affecting the target of 3rd level or lower end. For every spell ended in this way, the Taken King regains 4 (1d8) hit points.

Bite (Devil form only). Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) slashing damage plus 3 (1d6) poison damage.

Tail Spines (Devil form only). Ranged Weapon Attack: +5 to hit, range 20/80 ft., one target. Hit: 5 (1d4 + 3) piercing damage.

Paragon Traits
Paragon Fortitude. The Taken King has two pools of hit points, each of which is tracked separately. All damage and healing must be completely applied to only one pool. When a pool is reduced to zero, all ongoing conditions and effects affecting the Taken King end. Once a pool is reduced to zero, that pool cannot receive any healing until after a long rest. If all of the hit point pools are reduced to zero, the Taken King is killed.

Paragon Fury. The Taken King may take one additional turn in each round of combat if one of his hit point pools has been reduced to zero. The Taken King determines initiative normally for his first turn, though he gains advantage on the roll. If the Taken King has a second turn, it is inserted immediately after any one PC’s turn in the initiative order.

Paragon Transformation. The Taken King has two forms, each corresponding to one of the Taken King’s hit point pools. The Taken King begins the battle in its humanoid form. When that form’s hit point pool has been reduced to zero, he assumes his devil form immediately. Statistics, traits, or actions keyed to a specific form are only used when the Taken King is in that form.

[Ninja_Prawn]

Okay, the stat block is done. I'm quite pleased with it - your players should love the 'kill it in its humanoid form, only for it to transform into a flying devil' mechanic, and the two different forms present very different battlefield challenges. The humanoid form is a brawler with decent all-round stats, while the devil form is a flying pest that can flit around the battlefield (40 ft. movement, twice per round! No OAs when flying!) needling the PCs with spines and searing them if they get too close. It also makes it easy for you to have the thing escape at the end of the fight, given what you've said about this being an important villain.

One quick question: are you sure you need an equivalent to two spined devils? The 'Hard' encounter I made has three spined devils and three taken tieflings. Also, that encounter might not be hard enough for a boss fight, especially with all the magic items you've got floating around.

It will not necessarily be an easy task to add a third 'stage' to the above stat block...

Edit: oh, and I wasn't sure about how to handle all the resistances/immunities. I went with doubling the effective HP, but maybe you're supposed to apply the multiplier twice (quadruple HP). If this proves too strong in the game, the first change I would recommend would be to drop the damage immunities.

[1Forge]

Ninja_Prawn your a life saver. I took out one spined devil in the encounter because one my players dont get the magic items unless they can save the taken king (in which case he will reward them) and because some of our tanks might not be able to make it. If it got to easy I was just going to throw in something extra last second to make up for it. (like a shadow assassin they still haven't killed from the beginning of the game)

But seriously great help with CR's and balancing stat blocks! Its a real life saver. If you ever need help with something ill do my best to help with my limited resources :)

[Ninja_Prawn]

No problem, I'm happy to help. Hope it all works out ok!

[1Forge]

Things went weird. We had to delay the boss fight dude to most people having to leave early and our warlock opening a portal to hell (that exploded) and learning about an internal contract he made (sold 1/20th of his soul to his ancestor devil that already owns his soul...its complicated) and both our clerics not arriving at all. The taken minions have worked well though! And the taken king should work really well if the party shows up.

[Ninja_Prawn]

Cool, thanks for the update!

[1Forge]

Cool, thanks for the update!

Ok I finally finished the boss fight! It went well though instead we did it with a party of 5 two of which were 4th level 2 were 3rd and one was 2nd (he died) it was tough for them so i had to remove the taken spawn. Basically the cleric healed everyone as they nearly died all the time. The bard ran saving throw buffer, the wizard kept nailing it in the face with ray of frost, and the rogue spanked it over and over again. The illusionist died and he continued playing as an NPC guard with low stats (who tried to kick it once)