Mother of the Deep Coil

One-Shot · 6 PCs Lvl 12 · ~3–3.5 hrs · 2 encounters · Arima lair · Phase 3 Deadly

Style: Outer Brood → Multi-phase Echidna | Win: Echidna 0 HP

Ban: no Typhon · no Cerberus summons · Maguffin: Tripod Brand · QG: Melitta of Delphi

"When the Mother calls her children from the dark, press this ash-iron to the stone — the nest forgets one name." — Tripod Brand

Major Beats

Mist → Cilician foothills; Brand.
Enc. 1: Outer Brood; recruit Kimon; Short Rest only.
Enc. 2: Phase 1 Hard → Phase 2 Hard+ → Phase 3 Deadly.

Creature List

Creature	Use
Death Dog / Brood Harpy / Dracaena	Enc1 + summons
Orthrus (not Cerberus)	Phase 2
Chimera / Brood Sphinx	Phase 2–3
Lesser Brood-Hydra	Phase 3
Echidna Gargantuan	Boss HP 310

Difficulty

Tier	Adjust
As Written ★	6 PCs · APL 12
Library Standard	6 PCs · APL 8 — Reduce boss HP ~30–35%, strip one phase or one legendary action; minion counts −30%; Phase/Deadly language becomes Hard if present.
Easier	APL 10–11: use Library Standard, then remove the deadliest phase rider.
Harder	APL 13–15: restore full mythic pressure — extra phase or spawn; DCs +2.

ENC 1 — Outer Brood

Medium · 3 Death Dogs + 2 Harpies + 1 Dracaena · Kimon pinned

Non-combat: food/wine group AH/Pers 3 before 3 (DC 14); bribe dracaena 50 gp.
Heal/free Kimon → Enc2 Guide.
Brand 1/SR: disadv on one beast’s attacks vs wielder.
Short Rest only before descent.

ENC 2 — Phase Tracker

Phase 1 HP 310–207 · Call: 2 dogs or dracaena+harpy · Brand cancels 1 Call

Phase 2 HP 206–104 · Free Orthrus (or Sphinx) on entry · Coil Quake lair · Brand dismiss CR≤5 once

Phase 3 DEADLY HP 103–0 · Fear roar Wis DC 16 · Free Hydra (or Chimera+Orthrus) · +2 to hit · Bite poison DC 19 · LA Call cost 3 · Brand: 1 rd no Call + disadv Constrict

Summon caps: P1≤3 · P2≤4 · P3≤5 (Hydra = 2).
Win at Echidna 0 HP; summons flee.

STAT BLOCKS

Echidna CR14 BOSS

AC 17 | HP 310 | Gargantuan · LR 3

Bite +12 (3d8+7 +4d6 poison DC 18) · Constrict DC 20 · Tail Sweep · Call Brood R5–6 · Venom Spew · LA · Lair init 20

Orthrus CR5

Not Cerberus

AC 14 | HP 85 | Speed 50

2× Bite +7 + poison DC 14 · Double Maw R5–6 · Pack Howl

Chimera CR6

AC 14 | HP 114 | Fly 60

Bite/Horns/Claws +7 · Fire Breath R5–6 Dex DC 15 (7d8)

Brood-Hydra CR8

AC 15 | HP 150 · 5 heads

1 bite/head +8 · −30 HP = −1 head · Reactive heads

Death Dog CR1

AC 12 | HP 39

2× Bite +4 · poison/disease Con DC 12

Dracaena CR3

AC 14 | HP 68

Spear + Constrict · optional mercy warning

KEY ITEM / NPC

Tripod Brand of Arima

Enc1 1/SR: disadv vs brand-wielder 1 rd.
Enc2: 1/phase cancel Call or dismiss CR≤5; Phase 3 finale forbids Call 1 rd + disadv Constrict.

Melitta of Delphi

Pythia’s courier — Mother awake in Arima; mortals must end it.

Kimon

Recruit Enc1 → Guide / Warning Cry in nest.

Summon Ban

Never Typhon. Never Cerberus. Orthrus OK.

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