The Unforgotten Mere
Armor Class 16 (natural armor)
Hit Points 168 (16d10+80)
Speed 20 ft. swim 40 ft.
Saving Throws Con +9, Wis +7, Cha +8
Skills Insight +7, Deception +8, Perception +7
Damage Resistances bludgeoning; piercing; slashing from nonmagical attacks
Damage Immunities poison
Condition Immunities blinded, charmed, deafened, exhaustion, grappled, poisoned, prone, restrained
Senses blindsight 60 ft., passive Perception 17
Languages Common, Deep Speech, telepathy 120 ft.
Challenge 10 (5,900 XP) Proficiency Bonus +4
Actions
Bonus Actions
Reactions
Legendary Actions
The mere can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The mere regains spent legendary actions at the start of its turn.
Lair
Lair Actions
On initiative count 20 (losing initiative ties), the creature can take a lair action to cause one of the following effects; it can't use the same effect two rounds in a row:
- A Door That Wasn't There. A doorway, bridge, or stairway appears in a reflective surface within the lair. One creature within 60 feet must succeed on a DC 16 Wisdom saving throw or use its reaction to move up to 20 feet toward that surface. The image vanishes at the end of the round.
- Water Without Bottom. The mere fills a 20-foot-radius area it can see with impossible depth until initiative count 20 on the next round. The area is difficult terrain, and each creature that enters it or starts its turn there must succeed on a DC 17 Strength saving throw or be restrained until the start of its next turn.
- The Missing Detail. The mere erases one familiar detail from the minds of creatures in the lair. Each creature of the mere's choice must succeed on a DC 16 Intelligence saving throw or forget one nonessential fact about the current location until it leaves the lair, such as where an ally was standing, which passage it entered through, or what object it was carrying.
Regional Effects
The region containing the creature's lair is warped by its magic, creating the following effects:
- Within 6 miles of the mere, still water reflects places as they might have been rather than as they are.
- People who sleep within 1 mile of the mere dream of one regret fulfilled and wake with wet footprints beside their beds.
- Mirrors, windows, and polished metal near the mere occasionally show a missing person beckoning from the other side.
If the mere dies, its reflections become accurate over the course of 1d10 days, but every creature it drowned remains visible beneath nearby water until properly remembered and mourned.
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"Reach down. Your hands are still clean in the world below." — the voice of a drowned child
Lore & Description
Appearance
The Unforgotten Mere appears as a broad, motionless puddle of black-silver water, usually ten to twenty feet across. Its surface is perfectly smooth even in rain or wind, and it reflects a brighter, cleaner, more merciful version of the world around it. Pale blue lights drift beneath the surface like drowned stars. When it attacks, arms and faces rise from the water in translucent layers, each wearing the features of someone its victim has lost.
Behavior & Origins
The mere was once Elian Vey, a village well, a cherished family pond, or another beloved thing depending on the tale told nearby; in truth, it was the wishing pool beneath the vanished town of Bellwether, where generations cast coins and promises until grief, resentment, and abandoned hopes gathered into a living hunger. It does not understand why the world moved on without it, and it seeks to drown people inside perfect memories so they will never leave. The clearest hook is Bellwether's last survivor, Mara Quill, who keeps a rusted blue ferry bell and wants the mere named for what it truly was: the town's communal wishing well.
Running The Unforgotten Mere
Tactics
The mere begins with Reach for What Was Lost, targeting characters whose regrets it can exploit, then pulls the most vulnerable victim into range with Drowning Reflection. It stays spread across reflective surfaces, uses Borrowed Face to imitate an ally, and relies on its lair actions to separate the party. Once bloodied, it focuses on creatures that have learned its origin, attempting to drown them first; it fights to the death unless every reflective surface containing it is destroyed or consecrated.
DM Tips
- Telegraph the danger with puddles that reflect healed buildings, absent loved ones, or the characters themselves wearing different clothes, and with wet footprints leading away from otherwise dry water.
- Play the mere as intimate rather than loud: it speaks in remembered voices, finishes characters' sentences, and offers specific bargains instead of generic threats.
- Make the true-damage rule discoverable through witnesses, old records, or Mara Quill; attacks from ignorant characters still matter, but understanding the lost identity should feel like a tactical breakthrough.
- For a weaker party, remove the legendary action Remembered Wound and reduce the save DCs to 15; for a stronger party, let it occupy two disconnected reflective surfaces at once and give it 20 temporary hit points whenever a creature fails Reach for What Was Lost.
Loot
- Bellwether's Blue Ferry Bell — A palm-sized, rust-flecked bell that rings only near false reflections. If rung while naming a lost thing truthfully, it grants advantage on the next saving throw against the mere.
- Coin of the Last Wish — A silver coin bearing a worn image of Bellwether's well. Once per long rest, its bearer can cast augury, but the answer always includes one painful truth.
- Glass Tear — A translucent droplet that never evaporates. When held to the eye, it reveals the original form of a shapechanger or illusion for 1 minute, after which it cracks.
