Ancient Oblex

Gargantuan ooze, lawful evil

Armor Class 19 (natural armor)

19 (natural armor) Hit Points 390 (20d20 + 180)

390 (20d20 + 180) Speed 30 ft.

STR DEX CON INT WIS CHA 19 (+4) 22 (+6) 28 (+9) 26 (+8) 16 (+3) 21 (+5)

Saving Throws Dex +12, Con +15, Int +14, Cha +11

Dex +12, Con +15, Int +14, Cha +11 Damage Resistances bludgeoning, piercing, and slashing from nonmagical weapons

bludgeoning, piercing, and slashing from nonmagical weapons Condition Immunities blinded, charmed, deafened, exhaustion, prone

blinded, charmed, deafened, exhaustion, prone Senses blindsight 120 ft. (blind beyond this radius), passive Perception 19

blindsight 120 ft. (blind beyond this radius), passive Perception 19 Languages all

all Challenge 23 (50,000 XP)

Legendary Resistance (3/Day). If the oblex fails a saving throw, it can choose to succeed instead.

Amorphous. The oblex can move through a space as narrow as 1 inch wide without squeezing.

Aversion to Fire. If the oblex takes fire damage, it has disadvantage on attack rolls and ability checks until the end of its next turn.

Innate Spellcasting. The oblex's innate spellcasting ability is Intelligence (spell save DC 22). It can innately cast the following spells, requiring no material components:

At will: cause fear, charm person (as 7th-level spell), detect thoughts, hold person (as 5th-level spell), telekinesis

3/day each: confusion, dimension door, dominate person, fear, hallucinatory terrain, hold monster, hypnotic pattern

1/day each: dominate monster, mirage arcane

Master of Memories. The oblex is proficient in all skills, granting it a +6 bonus to any ability check it makes.

Sulfurous Impersonation. As a bonus action, the oblex can extrude a piece of itself that assumes the appearance of one Medium or smaller creature whose memories it has stolen. This simulacrum appears, feels, and sounds exactly like the creature it impersonates, though it smells faintly of sulfur. The oblex can impersonate 3d8 + 1 different creatures, each one tethered to its body by a strand of slime that can extend up to 240 feet away. For all practical purposes, the simulacrum is the oblex, meaning the oblex occupies its space and the simulacrum's space simultaneously. The slimy tether is immune to damage, but it is severed if there is no opening at least 1 inch wide between the oblex's main body and the simulacrum. The simulacrum disappears if the tether is severed.

Sulfurous Creation. As an action, the oblex can cast simulacrum and extrude a piece of itself that assumes the form of one Medium or smaller beast or humanoid whose memories it has stolen, without requiring material components. This simulacrum remains tethered to the oblex by a strand of slime that can extend up to 240 feet away, and the oblex can perceive through the simulacrum's senses.

The oblex cannot use this feature again until the simulacrum is reduced to 0 hit points or the oblex uses an action to reabsorb the simulacrum into itself. If the simulacrum is reduced to 0 hit points, the oblex can't create the same creature using this trait again.

Actions

Multiattack. The oblex makes four pseudopod attacks and uses Eat Memories.

Pseudopod. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 20 (4d6 + 6) bludgeoning damage plus 14 (4d6) psychic damage.

Eat Memories. The oblex targets one creature it can see within 10 feet of it. The target must succeed on a DC 22 Wisdom saving throw or take 66 (12d10) psychic damage and become memory drained until it finishes a short or long rest or until it benefits from the greater restoration or heal spell. Constructs, oozes, plants, and undead succeed on the save automatically.

While memory drained, the target must roll a d4 and subtract the number rolled from any ability check or attack roll it makes. Each time the target is memory drained beyond the first, the die size increases by one: the d4 becomes a d6, the d6 becomes a d8, and so on until the die becomes a d20, at which point the target becomes unconscious for 8 hours. The effect then ends.

When an oblex causes a target to become memory drained, the oblex learns all the languages the target knows and gains all its proficiencies, except any saving throw proficiencies. It also learns all of the target's class features, but can only make use of them with its Sulfurous Creation trait.

Legendary Actions

The oblex can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The oblex regains spent legendary actions at the start of its turn.

Attack. The oblex makes one pseudopod attack.

Move. The oblex moves itself and any number of its simulacra up to its speed.

Cast an At Will Spell (Costs 2 Actions). The oblex casts one of its at will spells.

Eat Memories (Costs 3 Actions). The oblex uses Eat Memories.