Large Monstrosity (Shapechanger), Chaotic Evil · CR 15 (13,000 XP) · BOSS · Deadly
AC 18 (natural) | HP 310 (27d10+162) | Speed 40 ft., climb 40 ft., swim 30 ft.
20 (+5)STR
18 (+4)DEX
22 (+6)CON
17 (+3)INT
18 (+4)WIS
22 (+6)CHA
Saves: Dex +9, Wis +9, Cha +11 · Skills: Deception +11, Perception +9, Stealth +9 · Resist: necrotic; nonmagical B/P/S · Condition Immunities: charmed, exhaustion, frightened · Senses: darkvision 120 ft., blindsight 30 ft. · Languages: Common, Sylvan · LR 3/day
Shapechanger. Bonus action to change between three forms; statistics are otherwise unchanged, and she reverts to Serpent-Coil at 0 HP. Queen (Medium) — the woman on Crisa’s coins; advantage on Deception against anyone who has seen them. Serpent-Coil (Large) — her true shape, woman to the hips and serpent below; Claws gain reach 10 ft. Night-Smoke — fly 40 ft. (hover), passes through any 1-inch gap, immune to nonmagical B/P/S, advantage on Dex saves; cannot attack, speak, or manipulate objects, and cannot enter running water or the Nursery.
Sleepless Regeneration. She regains 20 hit points at the start of her turn if she has at least 1 hit point and has taken no radiant damage and no damage from running water since the end of her last turn.
Sleepless. She cannot sleep, cannot gain exhaustion, and cannot be charmed or frightened. She has not rested in a season and it shows in everything she does.
Threshold-Bound. She cannot cross a doorway hung with a household’s wool threads unless invited across by someone who lives there. This is why she takes children out of doors. The threads on her own cave mouth are knotted from the inside — she tied them, around the last of her household.
A Mother’s Blindness. She cannot willingly harm Sibyl Herophile, cannot target her with any attack or effect, and will abort a cone, line, or area effect rather than catch her in it. A creature within 5 ft. of Herophile is inside that blind spot and cannot be included in her area effects either. Players will work this out. Let them.
Her Son in the Water (1/encounter). The first time Acheilus is visible to her inside the cave, she must succeed on a DC 20 Wisdom save or be stunned until the end of her next turn. She has been looking for him for a season, and he has been forty feet away the whole time.
Serpent Climb. She can climb difficult surfaces, including upside down on ceilings, without an ability check.
Actions
Multiattack. Three attacks, only one of which may be Drinking Bite.
Claw. +11 to hit, reach 5 ft. (10 ft. in Serpent-Coil). Hit: 16 (3d6+5) slashing, and a Large or smaller target is grappled (escape DC 17). She may hold two creatures at once.
Drinking Bite. +11 to hit, reach 5 ft., one creature that is grappled, restrained, incapacitated, or willing. Hit: 12 (2d6+5) piercing + 21 (6d6) necrotic (8d6 in Phase 2). The target’s hit point maximum is reduced by an amount equal to the necrotic damage and Lamia regains that many hit points; the reduction lasts until the target finishes a long rest. A creature reduced to a hit point maximum of 0 dies and rises 24 hours later as one of The Hollowed under her control. (DM: she does not keep what she drinks. It goes into Herophile.)
The Queen’s Welcome (Recharge 6). One creature within 30 ft. that can see her makes a DC 19 Wisdom save or is charmed for 1 hour. The charmed creature regards her as a trusted friend to be heeded and protected, and is a willing target for Drinking Bite. It repeats the save whenever Lamia or her allies do anything harmful to it, ending the effect on a success and becoming immune for 24 hours.
Call the Strix (Recharge 5–6; 4–6 in Phase 2). She summons 1 Strix Flock or 2 Hollowed into unoccupied spaces within 60 ft. They act on her initiative.
Bonus Actions
Shift Skin. Change form. Unavailable in Phase 2 except to enter Night-Smoke at 0 hit points.
Legendary Actions
Legendary Action Uses: 3 (4 in Lair). Immediately after another creature's turn ends, she can expend a use to take one of the following actions. She regains all expended uses at the start of each of her turns. All of Encounter 3 is her lair, so she runs at 4.
Drift (1). Move up to half her speed without provoking opportunity attacks; full speed in Night-Smoke.
Hungering Gaze (1). One creature within 30 ft. makes a DC 19 Wisdom save or has disadvantage on the next saving throw it makes against her before the end of her next turn.
Child-Voices (1). The cave answers in the voices of children. Each creature that can hear her within 60 ft. makes a DC 16 Wisdom save or is frightened of the sound until the end of its next turn; on a failure by 5 or more it also moves its full speed toward the deepest tunnel. A deafened creature is immune — including one she deafened herself with Owl-Cry.
Owl-Cry (2). Each creature of her choice within 30 ft. makes a DC 18 Constitution save or takes 14 (4d6) psychic damage and is deafened until the end of its next turn.
Drink (2). She makes one Drinking Bite attack against a valid target.
What She Wants (DM). Hera changed her family and did not kill it. Acheilus took the sea. Scylla went further out and has not come back. Herophile is the one Hera has not finished — or so her mother believes — and every drained calf, shepherd, and child on the Crisaean plain has gone into holding that off. She is not grieving. She is treating. She is also wrong: Herophile’s change already happened, and it was the prophecy.
Phase Thresholds. Phase 1: HP 310–156 — she is a hostess and a doctor, all charm and grapple economy. Phase 2: HP 155–0 — The Skin Comes Off: permanent Serpent-Coil, DC 18 Wis fear pulse on transition, +2 Hollowed and +1 Strix Flock arrive, Drinking Bite 8d6, +2 to hit. She stops arguing and starts feeding.
At 0 Hit Points. She collapses into Night-Smoke and streams for the Bier of Shed Skins. Intact and Eye-free → she reforms there in 1 hour with 50 HP. Destroyed or holding the Sleepless Eye → she is destroyed.
Persistence. Lamias are a species in this library, not a singular Olympian fixture — she may be killed. Hera never appears. Do not stage the goddess. Scylla never appears either — she is in open ocean, she is not coming, and that is the point of her.