D&D 4E 4e to 5e Balhannoth Conversion

ghabrel · Oct 9, 2016

So, yeah, title sums it up pretty well. Have a campaign I planted the seeds for back when 4e was a thing (I started on 4e, I didn't know it was garbage, I didn't know any better, please don't hold it against me), so now that I'm getting back around to it in 5e, I ran into the problem of the balhannoth monster not being listed in the 5e Monster Manual. Well, I figured no big deal, looked at the CR I wanted it to be at and whipped up a stat block based on that and the 4e entry for it. Would like some opinions on how balanced it is and if you all think it'll work well. Thanks in advance for anyone who chooses to comment. As always, if you like what you see, feel free to use it in your own campaigns. Here goes...

Balhannoth
Large Beast Aberration CR 23 (50,000 XP)
AC 19 HP 500 (40d10 + 280) Spd. 20’
-----Attributes-----
Str 29 (+9) Dex 27 (+8) Con 24 (+7)
Int 8 (-1) Wis 20 (+5) Cha 3 (-4)
-----Abilities-----
Skills Insight +12, Stealth +15
Senses blindsight 60 ft., passive Perception 15
Languages Deepspeech
Armor Natural
Proficiency +7
-----Special Abilities-----
Flailing Tentacles The balhannoth has six tentacles. If attacked directly, they have an AC of 17 and 61 (8d8 + 24) HP. If reduced to 0 HP, the tentacle is severed or otherwise neutralized (damage done to individual tentacles never applies to the balhannoth at any point). A neutralized tentacle takes a full day to regenerate, and cannot be used until then. Tentacles are never affected by area of effect attacks or spells. The balhannoth has a tendency to attempt to flee from fights in which three or more of its tentacles have been neutralized.
Invisibility As a bonus action, the balhannoth may become invisible until the end of its next turn or it makes an attack action.
Opportunist The balhannoth deals an extra 2d8 damage against targets it has combat advantage against.
Reality Shift The balhannoth may teleport up to 50 feet in place of its normal movement. Any enemies adjacent to it before it teleports are stunned for a full round, and the balhannoth automatically gains combat advantage against enemies it teleports adjacent to.
Spider Climb The balhannoth can climb across any surface, even upside down, as its full speed without the need for ability checks.
-----Actions-----
Multiattack: The balhannoth makes three tentacle attacks, and then it makes up to two slam and/or throw attacks.
Slam (Melee): +18, 15’, one or two targets.
Hit: The balhannoth must have at least one creature grappled with one of its six tentacles to make this attack. The balhannoth chooses one grappled creature to be the primary target, and then chooses to either bash the target against a nearby floor, wall, ceiling, or other hard surface; OR a second target, either also grappled or within 15 feet. If the attack only has one target, it deals 25 (3d8 + 18) bludgeoning damage; if it has two, it deals 21 (2d8 + 12) bludgeoning damage to both. In either case, the target(s) must pass a DC 20 Constitution saving throw or be stunned for a full round. The target(s) remain grappled.
Tentacle (Melee): +18, 15’, one target.
Hit: Target takes 13 (1d8 + 9) bludgeoning damage, and must pass a DC 20 Dexterity saving throw or be grappled by one of the balhannoth’s six tentacles. On its turn, the target may spend its action to try to pass a DC 20 Strength test to escape the grapple.
Throw (Ranged): +18, 30/60’, one or two targets.
Hit: The balhannoth must have at least one creature grappled with one of its six tentacles to make this attack. The balhannoth chooses one grappled creature to be the primary target, and then chooses to either throw the target against a nearby hard surface; OR at a second target within up to 60 feet. If there is only one target, the attack deals 25 (3d8 + 18) bludgeoning damage, and the target must pass a DC 20 Constitution saving throw or be knocked unconscious for 1d3 rounds. If there are two targets, the attack deals 21 (2d8 + 12) bludgeoning damage to both, and each must pass a DC 20 Constitution saving throw or be knocked prone and stunned for a full round On a hit, the primary target is thrown into a space adjacent to the secondary target. On a miss, it is thrown into a random square within 15 feet of the secondary target and knocked prone, and it is incapacitated on a failed save rather than being stunned.
Whipping Tentacles (Melee): +18, 15’, all targets within range.
Hit: Targets take 1d8 + 9 bludgeoning damage, and the balhannoth slides the target(s) to any other space within the area of effect.

ghabrel · Oct 9, 2016

Answer the poll! Give me some feedback! This monster was designed to be a solo encounter with 10 level 14 PCs and I don't know how to evaluate my own work! THE STRUGGLE IS REAL YOU GUISE!!!

DMZ2112 · Oct 9, 2016

My experience with both 14th level and monster creation in 5th Edition is limited, and I don't know the D&D4 balhannoth, but here goes.

My biggest concern is that this thing seems like no fun to fight. All that stunning amounts to a lot of annoyed players heading to the kitchen or the bathroom or starting side conversations at the table.

Opportunist needs some nerfing, too, because of all the stunning. Stun confers combat advantage. HP totals in D&D5 won't stand up to that kind of punishment.

Speaking of the stunning you ought to require more saving throws -- auto-stun is brutal. And you need to specify if "full round" means until the beginning or end of the balhannoth's next turn.

I'd just wholesale remove the unconsciousness effect from Throw. It's a cool ability but it is good enough without it.

I do think you ought to have more reaction abilities for a solo creature. In my experience, if a monster alone is waiting for its turn to act every round it is already dead. At 14th level, against a 19 AC, smart PCs have a >50% chance to hit every round, with multiple attacks or high-damage abilities. I'd give it max HP (680) in actual practice, and that still feels short.

Thematically I think you could give this thing greater than 5' reach, which would make its opportunity attacks a lot more dangerous.

Is Reality Shift intended to be usable every round? It feels more like a recharge ability.

I hope this was of some value.

ghabrel · Oct 9, 2016

[MENTION=78752]DMZ2112[/MENTION] Thank you very kindly for responding; I was getting antsy. Now let me go in order...

I did add some stuns. I can understand how those could be excruciatingly frustrating...

Opportunist was actually a direct grab from 4e. I don't remember 4e clearly enough to remember what combat advantage was back then, but I almost didn't include it because I didn't think it would be getting it often. That was before I transferred Reality Shift, and I wasn't even thinking about the advantage from stun until you mentioned it.

In all honesty, I completely made up the slam and throw attacks. I may have gotten a little carried away. It made sense to me that getting chucked into a wall by a giant, aberrant slug might knock you out. I'll reconsider that.

I never know what to give monsters as reactions. I even made some doppelganger variants with the Reactive feature (may make a reaction every turn), but didn't give them any special reactions. Any pointers you could give me there would be much appreciated.

As for the AC, the Quick Creation table never lists an AC above 19, so I was leery going over it. I'll think about adjusting the AC, or HP, or maybe even both...

The 15' reach is also a direct transfer from the 4e original, and now that you have me thinking about opportunity attacks, dropping Reactive on this sounds good. Especially if I can Slam or Throw as an opportunity... (Can I do that?)

Reality Shift is, again, directly from the original. In 4e, that's the only place the stuns come from, but it is an at-will, and the description even states that the balhannoth uses it repeatedly to strategically reposition itself. That leads me to my last point...

Even in 4e, a balhannoth is a BAMF. I had a decent idea of that just from its entry, but reading 4e forum posts I was going through trying to find another 5e version to compare it to just rammed it home. The old balhannoth was nothing to be trifled with, and I didn't want my version to be, either.

To give you a little context, my plan for encounters leading up to this one? None. None whatsoever. They would be going through a previously infested tunnel system while a mysterious, magical alarm grows from an imperceptible whine to a howling screech, which suddenly falls eerily silent when they discover the source. Moments later, a massive splash is heard echoing through the chambers as the balhanoth begins hunting its prey...

Thank you again so much for responding, and I hope you won't mind replying again!

DMZ2112 · Oct 9, 2016

ghabrel said:
Opportunist was actually a direct grab from 4e.

2d8 is a lot of bonus damage in D&D5. I would reduce the damage to 1d8 and remove some stuns.

In all honesty, I completely made up the slam and throw attacks. I may have gotten a little carried away. It made sense to me that getting chucked into a wall by a giant, aberrant slug might knock you out. I'll reconsider that.

I actually really like Throw. I think you could base the whole monster around that ability. My objection to the unconsciousness is not thematic -- it just isn't fun. You might be able to salvage it if PCs got a save every round and other PCs could kick them awake.

I never know what to give monsters as reactions.

When in doubt, just give the monster extra attacks of opportunity. Particularly, in this case, you want to simulate the balhannoth's multiple tentacles all attacking independently. Generally, in D&D5, everyone only gets one opportunity attack. So having more than one is a big advantage, especially with increaesd reach.

The 15' reach is also a direct transfer from the 4e original, and now that you have me thinking about opportunity attacks, dropping Reactive on this sounds good. Especially if I can Slam or Throw as an opportunity... (Can I do that?)

D&D5 doesn't really have 'basic attacks,' which is I think what you are asking, but considering that Slam and Throw both require a previously grappled target I am not sure how that would work. How does a grappled target trigger an attack of opportunity?

Reality Shift is, again, directly from the original. In 4e, that's the only place the stuns come from, but it is an at-will, and the description even states that the balhannoth uses it repeatedly to strategically reposition itself.

My gut says it is too much. Personally I'd put it on a recharge and grant a save against the stun.

To give you a little context, my plan for encounters leading up to this one? None. None whatsoever.

Click to expand...

A solo encounter is a tough thing to balance, and a solo encounter with the party at full strength even more so. The fact is that against a 14th-level party, fresh out of a long rest, there is very little any monster alone can do to prevent its imminent demise. The line between capable, intimidating solo monster and TPK is extremely thin.

The best advice I can give you depends heavily on the kind of campaign you are running. If you are big on simulation, take what suggestions you like, run the encounter, and prepare for either PC death or a disappointing show. If you are running a more narrative campaign, undershoot your damage output and don't give the balhannoth a hit point total. Run the encounter until the party is exhausted and then let them kill it.

Boss monsters are great for video games but D&D is just not designed to cope. Every rule there's ever been to support this kind of thing has been an ugly hack. Six vs. one only works when you're willing to have every fight be an endurance test.

Click to expand...

Jester David · Oct 9, 2016

ghabrel said:
I started on 4e, I didn't know it was garbage, I didn't know any better, please don't hold it against me

4e wasn't my jam, but far be it from me to cast aspersions on how people got started or what edition they like best. Do what you love.

ghabrel said:
so now that I'm getting back around to it in 5e, I ran into the problem of the balhannoth monster not being listed in the 5e Monster Manual. Well, I figured no big deal, looked at the CR I wanted it to be at and whipped up a stat block based on that and the 4e entry for it. Would like some opinions on how balanced it is and if you all think it'll work well.

Okay, the original (in Monster Manual IV for 3.5e was CR 10ish) while the Monster Manual for 4e was a level 13 elite lurker. So a conversion should aim for that level range. Somewhere around CR 8 to 15. It's not a god, so 23 seems like overkill. A variant (an elder balhannoth) might work.

The stats seem the same (except Int and Charisma were flipped). This isn't necessary: 4e had number creep with ability scores that isn't reflected in 5e. I'd make the Strength 21, Dex 20, Con 18, Wisdom 16. That's more than high enough.

The tentacles don't really need a description of being severed. Most monsters with tentacles don't have that.

I'd make the teleport an action. Or a bonus action. Replacing movement doesn't happen.

The attacks need to follow the 5e format. The target line for slam and throw could read Target: one creature grappled by the balhannoth. Which is my general advice: look at the Monster Manual and how it's monster statblocks are written and formatted.

It could probably also use a bite attack.

The creature lacks a unique power or effect. The 4e version is rather generic. Replacing invisibility with natural camouflage might be interesting. The Wikipedia entry mentions anti-magic. An aura where people who start in the zone have to make a save to cast a spell or use/trigger a magic item's power might be neat.

ghabrel · Oct 9, 2016

[MENTION=78752]DMZ2112[/MENTION] Thank you again for keeping up the dialog. I do really appreciate it.

So here's an updated stat block. I'll respond afterwards.

Balhannoth
Large Beast Aberration CR 23 (50,000 XP)
AC 19 HP 802 (24d20 + 280) Spd. 20’
-----Attributes-----
Str 29 (+9) Dex 27 (+8) Con 24 (+7)
Int 8 (-1) Wis 20 (+5) Cha 3 (-4)
-----Abilities-----
Skills Insight +12, Stealth +15
Senses blindsight 60 ft., passive Perception 15
Languages Deepspeech
Armor Natural
Proficiency +7
-----Special Abilities-----
Flailing Tentacles The balhannoth has six tentacles. If attacked directly, they have an AC of 17 and 61 (8d8 + 24) HP. If reduced to 0 HP, the tentacle is severed or otherwise neutralized (damage done to individual tentacles never applies to the balhannoth at any point). A neutralized tentacle takes a full day to regenerate, and cannot be used until then. Tentacles are never affected by area of effect attacks or spells. The balhannoth has a tendency to attempt to flee from fights in which three or more of its tentacles have been neutralized.
Flurry of Blows The balhannoth may make two opportunity attacks instead of one.
Invisibility As a bonus action, the balhannoth may become invisible until the end of its next turn, or until it makes an attack action.
Opportunist The balhannoth deals an extra 1d8 damage against targets it has advantage on attack rolls against.
Reactive The balhannoth can take one reaction on every turn in a combat.
Reality Shift (1/4Rd.) The balhannoth may teleport up to 50 feet in place of its normal movement. Any enemies adjacent to it before it teleports are stunned until the balhannoth’s next turn unless they pass a DC 20 Wisdom saving throw, and the balhannoth automatically gains advantage on attack rolls against enemies it teleports adjacent to.
Spider Climb The balhannoth can climb across any surface, even upside down, at its full speed without the need for ability checks.
-----Actions-----
Multiattack: The balhannoth makes three tentacle attacks, and then it makes up to two slam and/or throw attacks if able.
Slam (Melee): +18, 15’, one or two targets.
The balhannoth must have at least one creature grappled with one of its six tentacles to make this attack.
Hit: The balhannoth chooses one grappled creature to be the primary target, and then chooses to either bash the target against a nearby floor, wall, ceiling, or other hard surface; OR a second target, either also grappled or within 15 feet. If the attack only has one target, it deals 25 (3d8 + 18) bludgeoning damage; if it has two, it deals 21 (2d8 + 12) bludgeoning damage to both. If the secondary target isn’t grappled, it must pass a DC 20 Constitution saving throw or be knocked prone. The primary (and secondary) target(s) remain grappled.
Tentacle (Melee): +18, 15’, one target.
Hit: Target takes 13 (1d8 + 9) bludgeoning damage, and must pass a DC 20 Dexterity saving throw or be grappled by one of the balhannoth’s six tentacles. On its turn, the target may spend its action to try to pass a DC 20 Strength test to escape the grapple.
Throw (Ranged): +18, 30/60’, one or two targets.
The balhannoth must have at least one creature grappled with one of its six tentacles to make this attack.
Hit: The balhannoth chooses one grappled creature to be the primary target, and then chooses to either throw the target against a nearby hard surface; OR at a second target within up to 60 feet. If there is only one target, the attack deals 25 (3d8 + 18) bludgeoning damage, and the target must pass a DC 20 Constitution saving throw or be stunned until the balhannoth’s next turn. If there are two targets, the attack deals 21 (2d8 + 12) bludgeoning damage to both, and the secondary target must pass a DC 20 Constitution saving throw or be knocked prone (the primary target is automatically knocked prone). On a hit, the primary target is thrown into a space adjacent to the secondary target. On a miss, it is thrown into a random space within 15 feet of the secondary target and knocked prone, but takes no damage.
Whipping Tentacles (Melee): +18, 15’, all targets within range.
Hit: Targets take 1d8 + 9 bludgeoning damage, and the balhannoth slides the targets to any other space within the area of effect.

Again going in order.

2d8 is a lot of bonus damage in D&D5. I would reduce the damage to 1d8 and remove some stuns.

Bonus dropped to 1d8, some stuns removed.

I actually really like Throw. I think you could base the whole monster around that ability. My objection to the unconsciousness is not thematic -- it just isn't fun. You might be able to salvage it if PCs got a save every round and other PCs could kick them awake.

No unconsciousness, and the only possibility of a stun comes when thrown against something hard.

When in doubt, just give the monster extra attacks of opportunity. Particularly, in this case, you want to simulate the balhannoth's multiple tentacles all attacking independently. Generally, in D&D5, everyone only gets one opportunity attack. So having more than one is a big advantage, especially with increased reach.

Gave the balhannoth the existing Reactive feature and created the Flurry of Blows feature to ensure it always has plenty of opportunity attacks.

D&D5 doesn't really have 'basic attacks,' which is I think what you are asking, but considering that Slam and Throw both require a previously grappled target I am not sure how that would work. How does a grappled target trigger an attack of opportunity?

Yeah, you got to the heart of my confusion. And to clarify, I meant using Slam and Throw against targets provoking the opportunity attacks, not the grappled targets (i.e. just get extra damage by hitting two targets).

My gut says it is too much. Personally I'd put it on a recharge and grant a save against the stun.

Now once every 4 rounds, and the stun can be saved against.

A solo encounter is a tough thing to balance, and a solo encounter with the party at full strength even more so. The fact is that against a 14th-level party, fresh out of a long rest, there is very little any monster alone can do to prevent its imminent demise. The line between capable, intimidating solo monster and TPK is extremely thin.

The best advice I can give you depends heavily on the kind of campaign you are running. If you are big on simulation, take what suggestions you like, run the encounter, and prepare for either PC death or a disappointing show. If you are running a more narrative campaign, undershoot your damage output and don't give the balhannoth a hit point total. Run the encounter until the party is exhausted and then let them kill it.

I actually really like the idea of not having a HP total. That's more what I'm aiming for. Just throw something at them to show them they aren't the biggest kids on the playground...

Thank you so much. You've been a huge help. I really, really, genuinely appreciate your feedback.

ghabrel · Oct 10, 2016

[MENTION=37579]Jester David[/MENTION] Thank you for your input.

Okay, the original (in Monster Manual IV for 3.5e was CR 10ish) while the Monster Manual for 4e was a level 13 elite lurker. So a conversion should aim for that level range. Somewhere around CR 8 to 15. It's not a god, so 23 seems like overkill. A variant (an elder balhannoth) might work.

I got CR 23 by figuring out how a solo monster would make for a deadly encounter for 10 level 14 PCs, which is how I intend on using it. It was only after the fact that I realized ancient dragons are in the 23 CR range...

The stats seem the same (except Int and Charisma were flipped). This isn't necessary: 4e had number creep with ability scores that isn't reflected in 5e. I'd make the Strength 21, Dex 20, Con 18, Wisdom 16. That's more than high enough.

I never really got familiar enough with 4e to notice the stat creep, although I was definitely surprised by how high they were (yeah, I did just use the same stats as the 4e version with an Int-Wis swap).

The tentacles don't really need a description of being severed. Most monsters with tentacles don't have that.

Part of that was based off of the Roper entry, but another good part of it was to give the balhannoth a reason for leaving a fight before murdering all the PCs.

I'd make the teleport an action. Or a bonus action. Replacing movement doesn't happen.

A bonus action does sound rather fair, actually. It's the use of an action that still allows the balhannoth to make an attack afterwards.

The attacks need to follow the 5e format. The target line for slam and throw could read Target: one creature grappled by the balhannoth. Which is my general advice: look at the Monster Manual and how it's monster statblocks are written and formatted.

That is a fair point. Tomorrow I'll look over how the Monster Manual templates attacks and post an updated stat block.

It could probably also use a bite attack.

I've thought about both that and a constrict attack, but neither really seemed like it would be a beneficial trade-off over its existing attacks.

The creature lacks a unique power or effect. The 4e version is rather generic. Replacing invisibility with natural camouflage might be interesting. The Wikipedia entry mentions anti-magic. An aura where people who start in the zone have to make a save to cast a spell or use/trigger a magic item's power might be neat.

While I like and might consider an anti-magic type aura, I feel like the opportunity attack abilities I gave the balhannoth in the post after yours make it unique enough for me. I probably will replace the invisibility with some sort of passive camouflage or something though.

Thank you again for your feedback! I'll be sure to implement some of your suggestions.

ghabrel · Oct 10, 2016

Modified stat block to show changes after reading [MENTION=37579]Jester David[/MENTION] 's post:

Balhannoth
Large Beast Aberration CR 23 (50,000 XP)
AC 19 HP 742 (24d20 + 280) Spd. 20’
-----Attributes-----
Str 23 (+6) Dex 21 (+5) Con 18 (+4)
Int 8 (-1) Wis 16 (+3) Cha 3 (-4)
-----Abilities-----
Skills Insight +10, Stealth +12
Senses blindsight 60 ft., passive Perception 15
Languages Deepspeech
Armor Natural
Proficiency +7
-----Special Abilities-----
Flailing Tentacles The balhannoth has six tentacles. If attacked directly, they have an AC of 17 and 61 (8d8 + 24) HP. If reduced to 0 HP, the tentacle is severed or otherwise neutralized (damage done to tentacles never applies to the balhannoth). A neutralized tentacle takes a full day and a long rest to regenerate, and cannot be used until then. The tentacles are never affected by area of effect attacks or spells. The balhannoth has a tendency to attempt to flee from fights in which three or more of its tentacles have been neutralized.
Flurry of Blows The balhannoth may make two opportunity attacks instead of one, the second of which may but is not required to target a creature other than the one that provoked the opportunity attack.
Opportunist The balhannoth deals an extra 1d8 damage against targets it has advantage on attack rolls against.
Reactive The balhannoth can take one reaction on every turn in a combat.
Reality Shift (1/4Rd.) The balhannoth may teleport up to 50 feet as a bonus action. Any enemies adjacent to it before it teleports are stunned until the end of the balhannoth’s next turn unless they pass a DC 20 Wisdom saving throw, and the balhannoth automatically gains advantage on attack rolls against enemies it teleports adjacent to.
Spider Climb The balhannoth can climb across any surface, even upside down, at its full speed without the need for ability checks.
Stone Camouflage While in areas of natural or worked stone, the balhannoth has advantage on Dexterity (Stealth) checks.
-----Actions-----
Multiattack: The balhannoth makes three tentacle attacks, and then it makes up to two slam and/or throw attacks if able.
Slam (Melee): +18, 15’, one target.
The balhannoth must have at least one creature grappled with one of its six tentacles to make this attack.
Hit: The balhannoth chooses one grappled creature to bash against the target, dealing 21 (2d8 + 12) bludgeoning damage to both creatures. The grappled creature remains grappled, and the target must pass a DC 20 Strength saving throw or be knocked prone.
Tentacle (Melee): +18, 15’, one target.
Hit: The target takes 13 (1d8 + 9) bludgeoning damage, and must pass a DC 20 Dexterity saving throw or be grappled by one of the balhannoth’s six tentacles. On its turn, the target may spend its action to try to pass a DC 20 Strength test to escape the grapple.
Throw (Ranged): +18, 30/60’, one target.
The balhannoth must have at least one creature grappled with one of its six tentacles to make this attack.
Hit: The balhannoth chooses one grappled creature to fling at the target, dealing 31 (3d8 + 18) bludgeoning damage to both creatures and knocking them prone. The previously grappled creature lands in a space adjacent to the target, and both creatures must pass a DC 20 Constitution saving throw or be stunned until the end of the balhannoth’s next turn.
Miss: The balhannoth flings the chosen grappled creature within 15 feet of the target, knocking the previously grappled creature prone but dealing no damage to it.
Whipping Tentacles (Melee): +18, 15’, all targets within range.
Hit: The targets take 13 (1d8 + 9) bludgeoning damage, and the balhannoth slides the targets to any other space within the area of effect.

Tony Vargas · Oct 10, 2016

IMHO, converting from 3e or 4e (which, unfortunatlely, are the only editions in which this thing supposedly existed, though honestly, I have no memory of it - camouflaged anti-magic tentacled aberration on the ceiling? I'd expect something like that to stick with me), is usually wasted effort. Design it for 5e as if it were an original monster that just came to you in a nightmare.

Which is to say, don't really design it at all. Ballpark the hps, decide on an AC, and just have it do whatever seems sufficiently cool/terrifying each round, react to the the things the PCs do dramatically, and have fun with it until you reach that tipping point where the monster had better die or the players'll get bored, and have it drop at an appropriate moment. I know, that's terrible of me to even suggest such a blatant use of DM force.

But it works, often a lot better than trying to come up with a 'right' set of numbers.

OK, that out of the way:

ghabrel said:
Balhannoth
Large Beast Aberration CR 23

Sheesh, what level are you running?

Flailing Tentacles The balhannoth has six tentacles. If attacked directly, they have an AC of 17 and 61 (8d8 + 24) HP. If reduced to 0 HP, the tentacle is severed or otherwise neutralized (damage done to tentacles never applies to the balhannoth).

Fun, classic stuff, here, the monster with different body parts having different AC and separate hps. Definitely keep that. It could also mitigate against the issues 5e has with lone monsters.

"If attacked directly" should mean AEs only affect the body, not the tentacles. Otherwise it'd be too easy to blow 'em all off.

Flurry of Blows The balhannoth may make two opportunity attacks instead of one...
Reactive The balhannoth can take one reaction on every turn in a combat.

That sounds awesome in 5e's parsimonious action economy. You could also make it Legendary and give it Lair Actions, since it's a very lair kinda critter.