This deranged supra-genius was fun to play. Thought Disruption almost killed my party. I also decided to customise the treasure that the shipmind shares with the players:
Illithid Rubicite Armour. This +3 mind flayer splint mail is made from a crystalline substance and is very light (1/2 the weight of normal splint mail). Despite this it does not restrict movement breaking apart and instantly reconstituting itself to allow for articulation. Its ruby red in colour. Scholars have named the alien substance rubicite.
Armor Class 17 (container adds +3 armour) plus thought disruption
Hit Points (container) 240 with 10 hardness
Hit Points 136 (16d12 + 32)
Speed 0 ft. or 10 ft. (limited mobility)
Initiative Speed +2 (Dex +2)
STR 17 (+3) DEX 18 (+4) CON 14 (+2)
INT 21 (+5) WIS 21 (+5) CHA 21 (+5)
Saving Throws Dex +7, lnt +9, Wis +9, Cha +9
Skills Cybertheurgy +13, Deception +9, Insight +9, Perception +9
Damage Resistances cold, fire, lightning; bludgeoning, piercing, and slashing from nonmagical weapons
Damage Immunities acid, poison
Condition Immunities charmed, poisoned
Senses truesight 120 ft., passive Perception 19
Languages Abyssal, Aklo, Common, Draconic, Infernal, Undercommon, Protean; telepathy 120ft.
Challenge 12 (8,400)
Amorphous. The shipmind can move through a space as narrow as 1 inch wide without squeezing.
Container. A shipmind dwells within an immobile container of partially organic material grown by its Dominion masters. This container functions somewhat like a suit of armor for the shipmind. A shipmind container has hardness 10 and 240 hit points, and can be damaged by sunder attempts. A shipmind container that gains the broken quality grants only a +5 armor bonus to the shipmind within, and does not allow the shipmind to heal negative levels gained during a prolonged period outside of the container (see Limited Mobility). The partially crystalline nature of a shipmind container makes it vulnerable to shatter spells, and sonic damage bypasses the container’s hardness and inflicts full damage.
Limited Mobility. Unlike most oozes, a shipmind cannot exist outside of the partially organic container it was originally created in—this container serves the shipmind as its “skin.” While inside its container, a shipmind has a speed of 0 feet. When it leaves its container, it gains a speed of 10 feet, but loses its armor bonus to AC. A shipmind can exist outside of its container for 1 hour without consequences, but at the start of each subsequent hour it gains 1 level of exhaustion as its body starts to dissolve. This exhaustion cannot be restored by any means save by returning to an appropriate shipmind container, at which point they are removed at a rate of 1 level per hour.
Ship Interface. As long as a shipmind is interfaced with a Dominion vessel, it can observe events within the ship or within 90 feet of its exterior hull as if via clairaudience/ clairvoyance for as long as the shipmind concentrates. While concentrating on an area, the shipmind can activate traps or other ship systems in the area as a bonus action; it can even converse with creatures in the area by vibrating the metal and strange membranes in the walls.
Thought Disruption. The substance that makes up a shipmind ooze is charged with alien psychic energy that is toxic to the minds of most life forms. A creature that willfully touches an ooze (via a touch attack, natural weapon attack, or unarmed strike) or is struck by its slam attack must make a DC 17 Wisdom save or gain 1 level of exhaustion.
Multiattack. The shipmind can make two pseudopod attacks and a single plasma bolt attack. In addition it may always make a psychic crush attack if available.
Plasma Bolt. Ranged Weapon Attack: +9 to hit, 300 ft., one target.
Hit: 30 (10d6) plasma (fire and lighting) damage.
Pseudopod. Melee Weapon Attack: +8 to hit, reach 10 ft., one target.
Hit: 21 (5d6 + 3) bludgeoning damage plus thought disruption. If the target is a size Large or smaller, it is grappled (escape DC 17). Until this grapple ends, the target is restrained, and the shipmind looses a pseudopod attack.
At the start of the shipminds next turn it pulls the grappled creature into its container and immerses it into the pool of psychic and acidic soup. The creature takes 21 (6d6) plasma damage and is engulfed. The engulfed creature can’t breathe, is restrained, and takes 21(6d6) plasma damage at the start of each of the shipmind’s turns. An engulfed creature can try to escape by taking an action to make a DC 16 Strength check. On a success, the creature escapes and enters a space of its choice within 5 feet of the container. If the container has been destroyed the creature has advantage on this check.
Psychic Crush (Recharge 5-6). The shipmind targets one creature that it can sense within 60 feet of it. The target must make a DC 17 Intelligence saving throw, taking 21 (6d6) psychic damage on a failed save, or half as much damage on a successful one.
This yellowy viscous liquid bubbles in a large tank suspended by strangely organic cables. Wisps of white gas occasionally escape the roiling fluid.