Hello - I was wondering if all you great DM's out there could help me with something. I am picking up a campaign for a friend of mine only to run for 2 sessions. I am a player in the game but we are switching places for this already on-going 2E game.
I am looking for an underdark boss that should involve mind flayers. However, the party consists of players that are between 7th and 10th level characters (and 1 player with a 16th level dwarf/cleric). 

I am sending the party into Gracklstugh and into the worm tunnels where I will stage the final battle and to retrieve the item they are looking for. My question is, against this party, how many mind flayers, what level mind flayers? OR do I add a Beholder? Or maybe an Elder brain? I was steering away from an elder brain because I felt like that an elder brain would be more placed at a mind flayer hive deeper in the underdark and not at an outpost beneath Gracklstugh.

maybe a mindwitness ported to 2nd edition? they act like psionic telephone poles and it makes sense that they would be located near outposts

maybe a mind flayer Arcanist? again ported to 2e

Thanks, Capatin, if it were my campaign from the start, I'd go for it but otherwise, I'd want to keep 5E out of it, even though the mindwitness is from 3E

Just bumping this up..  :-)

Maybe use an Aboleth.

https://adnd2e.fandom.com/wiki/Aboleth

It may have some enslaved Underdark minions and might be also trying to take over the Mind Flayer Outpost. The party would offer a new wild-card front to that struggle between these psychic entities and could even be tempted or bribed to pick a side or fight both groups of monsters. However, whichever group they save for clearing out second might have had the breathing room to re-enforce and be ready.

Ithorak, The Abhorred Tyrant

Large Aberration (formerly Mind Flayer) Hit Dice: 12d8 + 60 (96 hp) Armor Class: 4 (natural armor) Movement: 30 ft., telepathy 120 ft.

THAC0: 10 (for a Medium target)
Attack Options:

• Tentacle Slam: +6 to hit, 1d6 + 6 damage
• Mind Blast: Save vs. Spell at -2 or be stunned
• Psionic Abilities: As detailed below

Special Attacks:

• Tentacle Slam: Ithorak uses its tentacles to strike at enemies. On a successful hit, the target must save vs. Paralyzation or be stunned for 1d4 rounds.
• Mind Blast: Ithorak can emit a powerful psionic wave. All creatures within 30 feet must make a saving throw vs. Spells at -2 or be stunned for 1d4 rounds. Ithorak can use this ability once every 3 rounds.
• Dominate Mind: Ithorak can attempt to control the mind of a single creature within 60 feet. The target must make a saving throw vs. Spells at -2 or be dominated as if by the spell Dominate Monster. This ability can be used once per day.

Special Defenses:

• Psionic Resistance: Ithorak is immune to psionic attacks and has a 50% resistance to all mind-affecting spells.
• Spell Immunity: Ithorak is immune to Charm Person, Hold Person, Sleep, and Confusion.

Psionic Abilities (20 PSPs):

• Detect Thoughts (1 PSP): Ithorak can read surface thoughts of creatures within 60 feet.
• Telekinesis (3 PSP): Ithorak can move objects or creatures weighing up to 300 pounds with its mind.
• Mind Link (4 PSP): Ithorak can establish a telepathic link with any creature it can see within 60 feet, allowing silent communication.
• Plane Shift (10 PSP): Ithorak can transport itself and up to 6 other willing creatures to another plane of existence, as per the spell Plane Shift. This ability is usable once per week.

Saving Throws:

• Paralyzation, Poison, or Death Magic: +2
• Petrification or Polymorph: +2
• Wands: +2
• Breath Weapons and Spells: +2

Alignment: Lawful Evil
Skills:

• Psionics: Master
• Arcane Knowledge: Proficient

Description:
Ithorak, known as The Abhorred Tyrant, was once a powerful mind flayer who transcended its kind’s limitations through dark rituals and psionic enhancements. Now a twisted abomination, Ithorak rules an ancient, labyrinthine section of the Underdark with an iron grip. It uses its psionic prowess and illithid legacy to dominate and terrorize all who enter its domain. Ithorak's lair is filled with mind-controlled thralls and mind flayer cultists, reflecting its enduring influence and power.

Tactics:
Ithorak will use its Mind Blast to incapacitate foes before closing in with its tentacles. It will attempt to Dominate key enemies to turn the tide of battle in its favor. It utilizes its Psionic Abilities to manipulate and control the battlefield, retreating only if critically threatened or if its plans are thwarted.

Lair:
Ithorak resides in a vast, ancient cavern deep in the Underdark. Its lair is filled with traps and psionically dominated creatures that serve as both guards and sacrifices for Ithorak’s dark rituals.

This is the big boss. Feel free to adjust if you want

I'm not holding in 2E, but if mind flayers in 2E resemble the way they work in 5E, multiple mind flayers will be a problem. They all have dominate person, which means that there becomes a real possibility of the majority of the party being dominated, at which point they're sunk.

I'd go with a single boss mind flayer, with inflated stats, and a bunch of enspelled minions.

Quote from IMPLAYS >>

Ithorak, The Abhorred Tyrant

Large Aberration (formerly Mind Flayer) Hit Dice: 12d8 + 60 (96 hp) Armor Class: 4 (natural armor) Movement: 30 ft., telepathy 120 ft.

THAC0: 10 (for a Medium target)
Attack Options:

• Tentacle Slam: +6 to hit, 1d6 + 6 damage
• Mind Blast: Save vs. Spell at -2 or be stunned
• Psionic Abilities: As detailed below

Special Attacks:

• Tentacle Slam: Ithorak uses its tentacles to strike at enemies. On a successful hit, the target must save vs. Paralyzation or be stunned for 1d4 rounds.
• Mind Blast: Ithorak can emit a powerful psionic wave. All creatures within 30 feet must make a saving throw vs. Spells at -2 or be stunned for 1d4 rounds. Ithorak can use this ability once every 3 rounds.
• Dominate Mind: Ithorak can attempt to control the mind of a single creature within 60 feet. The target must make a saving throw vs. Spells at -2 or be dominated as if by the spell Dominate Monster. This ability can be used once per day.

Special Defenses:

• Psionic Resistance: Ithorak is immune to psionic attacks and has a 50% resistance to all mind-affecting spells.
• Spell Immunity: Ithorak is immune to Charm Person, Hold Person, Sleep, and Confusion.

Psionic Abilities (20 PSPs):

• Detect Thoughts (1 PSP): Ithorak can read surface thoughts of creatures within 60 feet.
• Telekinesis (3 PSP): Ithorak can move objects or creatures weighing up to 300 pounds with its mind.
• Mind Link (4 PSP): Ithorak can establish a telepathic link with any creature it can see within 60 feet, allowing silent communication.
• Plane Shift (10 PSP): Ithorak can transport itself and up to 6 other willing creatures to another plane of existence, as per the spell Plane Shift. This ability is usable once per week.

Saving Throws:

• Paralyzation, Poison, or Death Magic: +2
• Petrification or Polymorph: +2
• Wands: +2
• Breath Weapons and Spells: +2

Alignment: Lawful Evil
Skills:

• Psionics: Master
• Arcane Knowledge: Proficient

Description:
Ithorak, known as The Abhorred Tyrant, was once a powerful mind flayer who transcended its kind’s limitations through dark rituals and psionic enhancements. Now a twisted abomination, Ithorak rules an ancient, labyrinthine section of the Underdark with an iron grip. It uses its psionic prowess and illithid legacy to dominate and terrorize all who enter its domain. Ithorak's lair is filled with mind-controlled thralls and mind flayer cultists, reflecting its enduring influence and power.

Tactics:
Ithorak will use its Mind Blast to incapacitate foes before closing in with its tentacles. It will attempt to Dominate key enemies to turn the tide of battle in its favor. It utilizes its Psionic Abilities to manipulate and control the battlefield, retreating only if critically threatened or if its plans are thwarted.

Lair:
Ithorak resides in a vast, ancient cavern deep in the Underdark. Its lair is filled with traps and psionically dominated creatures that serve as both guards and sacrifices for Ithorak’s dark rituals.

This is the big boss. Feel free to adjust if you want

 Wow! Did you create this for your game or something?

no I chatGPT"d it and then edited it myself. I had to do research into 2e because I just joined with 5e

Quote from IMPLAYS >>

no I chatGPT"d it and then edited it myself. I had to do research into 2e because I just joined with 5e

 Oh wow! Thank you! I'll have to see if I can come up with an image of this guy. I guess some slight modifications of a mind flayer.  Thank you very much!

Okay, someone help me out, because I really need to subdue my 16th level dwarf....who I am now finding out, is a 16/15 fighter / cleric.  (There is a reason behind all of this and I can explain if someone really wants to know) - 

BUT, I think Psionics is the only way I have a chance to subdue him while giving the rest of the party a bit of a challenge at least with some mind flayers and thralls? So, if I am going with Ithorak and the Psionic abilities, I have questions because I we have never really played with hardcore Psionics. 

So, are there saving throws for Psionics?  For example, if the creature wants to use telekinesis against another, does the intended target get a saving throw vs spells or something? 

Psionic Abilities (20 PSPs):

• Detect Thoughts (1 PSP): Ithorak can read surface thoughts of creatures within 60 feet.
• Telekinesis (3 PSP): Ithorak can move objects or creatures weighing up to 300 pounds with its mind.
• Mind Link (4 PSP): Ithorak can establish a telepathic link with any creature it can see within 60 feet, allowing silent communication.
• Plane Shift (10 PSP): Ithorak can transport itself and up to 6 other willing creatures to another plane of existence, as per the spell Plane Shift. This ability is usable once per week.

Well looking up Telekinesis:

You gain the ability to move or manipulate creatures or objects by thought. When you cast the spell, and as your action each round for the duration, you can exert your will on one creature or object that you can see within range, causing the appropriate effect below. You can affect the same target round after round, or choose a new one at any time. If you switch targets, the prior target is no longer affected by the spell.

Creature. You can try to move a Huge or smaller creature. Make an ability check with your spellcasting ability contested by the creature's Strength check. If you win the contest, you move the creature up to 30 feet in any direction, including upward but not beyond the range of this spell. Until the end of your next turn, the creature is restrained in your telekinetic grip. A creature lifted upward is suspended in mid-air.

On subsequent rounds, you can use your action to attempt to maintain your telekinetic grip on the creature by repeating the contest.

Object. You can try to move an object that weighs up to 1,000 pounds. If the object isn't being worn or carried, you automatically move it up to 30 feet in any direction, but not beyond the range of this spell.

If the object is worn or carried by a creature, you must make an ability check with your spellcasting ability contested by that creature's Strength check. If you succeed, you pull the object away from that creature and can move it up to 30 feet in any direction but not beyond the range of this spell.

You can exert fine control on objects with your telekinetic grip, such as manipulating a simple tool, opening a door or a container, stowing or retrieving an item from an open container, or pouring the contents from a vial.

So, spell ability vs Strength check looks like.

So, the "target" of the telekinesis must make a strength check, if I am trying to have the "boss" use his psionic abilities?  It works the same as the spell itself?

Quote from tonyd020 >>

So, the "target" of the telekinesis must make a strength check, if I am trying to have the "boss" use his psionic abilities?  It works the same as the spell itself?

 It should unless you have a different way you want it to work. 

So if the target has an 18 strength, it would be hard to make that psionic work on that player. 

I don't about psionics and how it works- we've never really played with it all that much if at all.

Quote from tonyd020 >>

So if the target has an 18 strength, it would be hard to make that psionic work on that player. 

I don't about psionics and how it works- we've never really played with it all that much if at all.

 Depends on how good the caster's spell ability check is (if you ae using 5th Ed rules). 

Assuming that the target has an 18 Str as is a 16h level character, you're general looking at a +9 to the d20 roll for the Strength/Athletics check. Contest that with a boss monster that has a +10 or +12 on the roll and it would be a little more difficult to succeed.

However if you are using 2nd Ed rules, I'd rule it more as just a Save vs. Spell and use the rules and numbers for that.