The tower's master, Archmage Ilyr Vhalanthis, attempted to preserve his mind after foreseeing the collapse of Netheril's remaining enclaves. He used the Starless Prison to store memories as crystalline patterns, believing that a consciousness could be rebuilt from its recollections. The ritual absorbed the prison's captives and produced the Mnemonic Wyrm. The lower-vault entity later imprisoned it, using its memory-feeding nature to erase intruders and conceal the route to the final sanctum. The wyrm now knows that the final sanctum contains proof that Ilyr's ritual was not an accident. The tower's master deliberately created a consciousness capable of replacing the entity that ruled the prison.
HP187AC+10SPDFly 40 feet, hover, Can move through creatures and objects as difficult terrain while using Half-Remembered Passage, Cannot cross a mnemonic anchor's boundary unless the anchor is deactivated or the wyrm succeeds on a DC 18 Charisma saving throwCR12 (8,400 XP)|ArcanaDeceptionHistoryInsightPerceptionStealth
STR
18
DEX
18
save
CON
18
save
INT
20
save
WIS
19
save
CHA
20
save
Legendary Resistance.The wyrm has advantage on saving throws against spells and other magical effects. If it fails a saving throw, it can choose to succeed instead twice per day.
Innate Spellcasting.The wyrm can cast its spells without material components. Its spellcasting ability is Intelligence.
Phase-Shifted Form.The wyrm can move through other creatures and objects as if they were difficult terrain. If it ends its turn inside an object, it takes 10 force damage. It cannot pass through a mnemonic anchor unless that anchor is deactivated.
Memory Anchors.At the start of each of its turns, the wyrm can teleport up to 30 feet to an unoccupied space adjacent to a stasis alcove, archive shelf, bridge anchor, or name-plate it can see.
Undead Persistence.The wyrm does not need to breathe, eat, drink, or sleep. It is immune to effects that would age it or force it to sleep.
Stolen Perspective.If a creature within 60 feet fails a saving throw against one of the wyrm's psychic effects, the wyrm gains 10 temporary hit points and can see through that creature's eyes until the end of the creature's next turn.
Prison Anchor.The wyrm has three mnemonic anchors in the chamber. While at least one remains active, the wyrm cannot be reduced below 1 hit point unless it is affected by purified oasis water or the stabilizing phrase. Each anchor can be disabled with an action and a successful Arcana, Investigation, or Religion check, or destroyed by dealing 25 damage to it. An anchor has AC 17 and 25 hit points.
Toxic Spell-Gas.The mnemonic wyrm exhales a 30-foot cone of toxic spell-gas. Each creature in the area must make a Constitution saving throw, taking 31 () poison damage and becoming poisoned for 1 minute on a failed save, or taking half damage and suffering no additional effect on a success. A poisoned creature that fails the save by 5 or more also forgets the last 10 minutes, losing awareness of events that occurred during that time. The creature can repeat the saving throw at the end of each of its turns, ending the poisoned condition on a success.
Thought-Eating Ray.Ranged Spell Attack: to hit, range 120 feet, one target. Hit: 27 () psychic damage, and the target must succeed on a Intelligence saving throw or be unable to remember the wyrm's current location until the end of its next turn. The wyrm can then teleport to an unoccupied space adjacent to a stasis alcove, archive shelf, or bridge anchor it can see.
Consume Recent Memory.The wyrm targets one creature it can see within 90 feet. The target must make a Wisdom saving throw. On a failure, the target takes 22 () psychic damage and forgets one fact, plan, name, or instruction learned during the current encounter. The target can recover the lost information if another creature spends an action reminding it, or after finishing a short or long rest. On a success, the target takes half damage and suffers no memory loss.
Unmake the Bridge.The wyrm targets one point on the stone bridge within 120 feet. A 10-foot square of the bridge buckles into a gravityless fracture until the end of the wyrm's next turn. A creature standing in that square must succeed on a Dexterity saving throw or fall prone and drift 20 feet toward the vault's central shaft. A creature can use an action to catch a chain, ledge, or ally within reach.
Archive Snare.The wyrm animates one nearby chain, name-plate, or archive shelf within 60 feet. One creature within 10 feet of the object must succeed on a Strength or Dexterity saving throw, chosen by the creature, or take 18 () force damage and become restrained until the end of the wyrm's next turn. The restraint ends early if the object takes 15 damage.
Flood of Borrowed Faces.The wyrm releases a stolen memory into a 20-foot-radius sphere centered on a point it can see within 90 feet. The area becomes heavily obscured by images of forgotten faces until the end of the wyrm's next turn. Creatures entering the area for the first time on a turn or starting their turn there must succeed on a Wisdom saving throw or become frightened until the start of their next turn.
Half-Remembered Passage.The wyrm moves up to its flying speed without provoking opportunity attacks. During this movement, it can pass through creatures and objects as if they were difficult terrain. The first creature it passes through must make a Constitution saving throw, taking 14 () psychic damage on a failure and suffering disadvantage on its next Intelligence, Wisdom, or Charisma check before the end of its next turn.
Trade a Memory.When a creature the wyrm can see succeeds on an Intelligence, Wisdom, or Charisma saving throw, the wyrm imposes disadvantage on the roll after seeing the result but before knowing whether it succeeds. The creature can choose to forget one detail it learned during the encounter to turn the roll into a success instead.
Drift Through Thought.The wyrm makes a Half-Remembered Passage attack or moves up to half its flying speed without provoking opportunity attacks.
Rewrite the Battlefield (Costs 2 Actions).The wyrm uses Archive Snare or Thought-Eating Ray.
Devour the Name (Costs 3 Actions).The wyrm uses Consume Recent Memory against one creature within 90 feet, even if it has already used that action this round.
1st level
CommandEnchantment— The wyrm targets up to three creatures it can see within 30 feet. Each target must make a DC 18 Wisdom saving throw or become charmed for 1 minute. A charmed target regards the wyrm as a trusted mentor and repeats the last sentence it heard.
2nd level
Phantasmal ForceIllusion— The wyrm targets one creature within 60 feet. The target must succeed on a DC 18 Intelligence saving throw or be unable to distinguish allies from enemies until the end of its next turn.
3rd level
ClairvoyanceDivination— The wyrm creates a magical sensor in an archive alcove, allowing it to observe and hear through the sensor within 1 mile for up to 10 minutes.
Major ImageIllusion— The wyrm creates a spectral duplicate of a creature whose name is engraved on a nearby name-plate. The duplicate lasts for 1 minute and can speak, distract, and mimic the creature, but cannot deal damage.
4th level
ConfusionEnchantment— The wyrm creates a 20-foot-radius sphere of psychic static for up to 10 minutes. Creatures inside have disadvantage on Intelligence checks and cannot communicate telepathically with creatures outside the sphere.
5th level
Modify MemoryEnchantment— The wyrm attempts to alter one creature's memory of an event from the last 24 hours. The effect is unstable and lasts only until the creature leaves the Starless Prison unless reinforced by the lower-vault entity.
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