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.

Mist opens on the Cilician foothills above the deep of Arima — where the Mother of Monsters coils in her own darkness. Clear the outer brood, descend the chimney, and endure three rising phases as Echidna calls her children. Press the brand when she calls a name you cannot afford.

Creature / Enemy List

Creature	Counts / Notes
Death Dog	2 · 3 · 4 · Enc. 1 / summons
Brood Harpy	2 · 3 · 4 · Enc. 1
Dracaena Guard	1 · 2 · 2 · Enc. 1
Orthrus	1 · 1 · Phase 2 summon
Chimera	0–1 · 1 · Phase 2–3
Brood-Hydra	1 · Phase 3
Echidna	adj · 1 · 1 · Boss

DM Tips

As Written ★ — 6 Players, Average Level 12: Baseline for this guide. Numbers, DCs, and win tracks assume six PCs at average level 12.
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.

Encounter 1 — The Outer Brood

🗺 Terrain 60×40 ravine · chimney entrance north (climb Ath DC 12 down 40 ft. after fight) · scree difficult terrain in two 10-ft patches. · Bone-littered ravine before the chimney. 3× Death Dogs + 2× Brood Harpies + 1× Dracaena Guard . Kimon is pinned under a collapsed goat-pen (½ cover).

Non-combat path: Offer meat/wine + Animal Handling/Persuasion group 3 successes before 3 failures (DC 14) to draw dogs off while the party slips to the chimney — still face 1 dracaena at the lip (or bribe her with treasure 50+ gp).
RECRUITMENT: Free/heal Kimon → Enc. 2 Guide / Warning Cry.
Brand : disadv on one brood-beast’s attacks vs. brand-wielder (1/SR).
Rest: Short Rest only at chimney mouth; something huge exhales below.
Tip: RECRUITMENT (optional). If reduced without a killing blow and offered mercy (Persuasion DC 15), one may hiss a warning about Phase 2’s Orthrus — then flees. Not a combat ally.
Tip: Medium Humanoid, Neutral Good · CR 1/2 · Recruitable
Tip: RECRUITMENT. Spare him / heal him in Enc. 1 (Medicine DC 12 or any healing). In Enc. 2 he can Guide once: party ignores difficult terrain from bone-scree for 1 round, or points out a ½-cover ledge.
Tip: Wondrous Item (maguffin), Unique

Encounter 2 — Mother of the Deep Coil (Multi-Phase)

Saves: Dex +7, Con +10, Wis +8 · Resist: poison, BPS nonmagical · Immune: poisoned · Senses: darkvision 120 ft. · LR 3/day · The nest opens: black pool, bone shelves, Echidna coiled half in water. She fights in three phases as HP falls. Budget this as the session’s main dish.

Echidna uses full Multiattack; Call Brood (R5–6): 2× Death Dogs or 1× Dracaena + 1× Harpy.
Lair actions on; Legendary Actions: Detect / Tail / Hiss (no Phase-3 Call).
Brand: cancel next Call Brood once this phase.
On transition (first time she enters this band): immediate free Call Brood — summon Orthrus (preferred) or Brood Sphinx .
Call Brood options expand: Orthrus, Chimera (if Orthrus already out, prefer 2 Death Dogs + Harpy), Dracaenae.
Lair: Coil Quake unlocked. Venom Spew preferred vs. clustered casters.
Brand: cancel one Call or dismiss one CR ≤5 summon on arrival (once this phase).
Deadly by design. On transition: roar — each enemy Wis DC 16 or frightened until end of its next turn; then free Call Brood: Lernean Brood-Hydra or Chimera + Orthrus if Hydra too heavy for your table.

DM Callouts

RECRUITMENT (optional). If reduced without a killing blow and offered mercy (Persuasion DC 15), one may hiss a warning about Phase 2’s Orthrus — then flees. Not a combat ally.
Medium Humanoid, Neutral Good · CR 1/2 · Recruitable
RECRUITMENT. Spare him / heal him in Enc. 1 (Medicine DC 12 or any healing). In Enc. 2 he can Guide once: party ignores difficult terrain from bone-scree for 1 round, or points out a ½-cover ledge.
Wondrous Item (maguffin), Unique

Extra Encounter Detail (from session guide)

ENC 2

Echidna gains +2 to hit; Bite poison DC 19; Call Brood legendary (cost 3) available.
Max summons raised; Hydra counts as 2 toward cap.

Quick combat reference

Death Dog (Two-Headed Brood) — AC 12 | HP 39 | Speed 40 ft. · Medium Monstrosity, Neutral Evil · CR 1 · Mini-optional
Brood Harpy — AC 11 | HP 38 | Speed 20 ft., fly 40 ft. · Medium Monstrosity, Chaotic Evil · CR 1
Dracaena Guard — AC 14 | HP 68 | Speed 30 ft. · Large Monstrosity, Neutral Evil · CR 3 · Echidna’s door-ward
Kimon the Goatherd-Scout — AC 12 | HP 18 | Speed 30 ft. · Medium Humanoid, Neutral Good · CR 1/2 · Recruitable
Echidna, Mother of Monsters — AC 17 (natural) | HP 310 (20d20+100) | Speed 40 ft., burrow 20 ft., swim 40 ft. · Gargantuan Monstrosity, Chaotic Evil · CR 14 (phases escalat
Orthrus — AC 14 | HP 85 | Speed 50 ft. · Large Monstrosity, Neutral Evil · CR 5 · Two-headed hound ·
Chimera — AC 14 | HP 114 | Speed 30 ft., fly 60 ft. · Large Monstrosity, Chaotic Evil · CR 6 · Classic brood-child

Additional DM notes

**Non-combat path:** Offer meat/wine + Animal Handling/Persuasion group 3 successes before 3 failures (DC 14) to draw dogs off while the party slips to the chimney — still face 1 dracaena at the lip (or bribe her with treasure 50+ gp).
**RECRUITMENT:** Free/heal Kimon → Enc. 2 Guide / Warning Cry.
**Brand**: disadv on one brood-beast’s attacks vs. brand-wielder (1/SR).
**Rest:** Short Rest only at chimney mouth; something huge exhales below.
15 (+2)**STR**14 (+2)**DEX**14 (+2)**CON**3 (−4)**INT**13 (+1)**WIS**6 (−2)**CHA
Not Cerberus.** Two-headed only — never stage as Cerberus.
12 (+1)**STR**13 (+1)**DEX**12 (+1)**CON**7 (−2)**INT**10 (+0)**WIS**13 (+1)**CHA
16 (+3)**STR**12 (+1)**DEX**14 (+2)**CON**8 (−1)**INT**12 (+1)**WIS**10 (+0)**CHA
RECRUITMENT (optional).** If reduced without a killing blow and offered mercy (Persuasion DC 15), one may hiss a warning about Phase 2’s Orthrus — then flees. Not a combat ally.
RECRUITMENT.** Spare him / heal him in Enc. 1 (Medicine DC 12 or any healing). In Enc. 2 he can Guide once: party ignores difficult terrain from bone-scree for 1 round, or points out a ½-cover ledge.

Pacing helpers

Enc 1: End by ~45–50 min; if stuck, telegraph the non-combat path once.
Enc 2: Spend recruitment / maguffin early so Enc 3 is not a blank check.
Enc 3: Keep Hard, not Deadly — drop a minion wave before a TPK spiral.

STAT BLOCKS

Echidna CR14 BOSS

AC 17 | HP 310 | Gargantuan · LR 3

	STR	DEX	CON	INT	WIS	CHA
sc md sv	24 +7 +7	14 +2 +7	20 +5 +10	14 +2 +2	16 +3 +8	18 +4 +4

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

	STR	DEX	CON	INT	WIS	CHA
sc md sv	18 +4 +4	14 +2 +2	16 +3 +3	4 −3 −3	12 +1 +1	7 −2 −2

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

Chimera CR6

AC 14 | HP 114 | Fly 60

	STR	DEX	CON	INT	WIS	CHA
sc md sv	19 +4 +4	11 +0 +0	17 +3 +3	3 −4 −4	14 +2 +2	10 +0 +0

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

Brood-Hydra CR8

AC 15 | HP 150 · 5 heads

	STR	DEX	CON	INT	WIS	CHA
sc md sv	20 +5 +5	12 +1 +1	20 +5 +5	2 −4 −4	10 +0 +0	7 −2 −2

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

Death Dog CR1

AC 12 | HP 39

	STR	DEX	CON	INT	WIS	CHA
sc md sv	15 +2 +2	14 +2 +2	14 +2 +2	3 −4 −4	13 +1 +1	6 −2 −2

2× Bite +4 · poison/disease Con DC 12

Dracaena CR3

AC 14 | HP 68

	STR	DEX	CON	INT	WIS	CHA
sc md sv	16 +3 +3	12 +1 +1	14 +2 +2	8 −1 −1	12 +1 +1	10 +0 +0

Spear + Constrict · optional mercy warning