Mother of the Deep Coil
One-Shot · 6 Players · Level 12 · ~3–3.5 Hours · 2 Encounters · Echidna Lair (Phase 3 Deadly)
📜 Session Summary
| Setting Cilician foothills ravine (bone-littered) → bone-chimney descent → gargantuan nest-cavern with black pool at Arima |
| Atmosphere Ancient predator darkness · the smell of old blood and wet stone · the understanding that something very large has been awake for a long time and is no longer interested in patience |
| Materials Ash-iron brand with Delphic laurel stamp, bone-scree, black pool water, serpent-shed scales, chimney-glow from below, pythia-ash in a sealed clay packet |
| Tone Mythic horror wearing the face of the familiar — these are monsters the party knows the names of, and the names do not help; the Brand is the only leverage and it has three uses |
| Style Lair Assault — Outer Brood skirmish → Multi-phase Echidna (Phase 3 Deadly) |
| Win Condition Defeat Echidna (0 HP) in her nest at Arima |
| Players 6 × Level 12 · Duration 3–3.5 hrs · Structure 2 encounters (Enc. 2 is long) |
| Override Final phase is Deadly (user request). No Typhon. No Cerberus among summons. |
| Maguffin Tripod Brand of Arima · QG: Melitta of Delphi |
Description
Melitta of Delphi arrives at the mist-line with a sealed clay packet smelling of laurel-smoke and a face that has been delivering terrible news for long enough to be very efficient about it. The Pythia has named what is happening at Arima: the Mother of Monsters, Echidna, has woken in her deep coil beneath the Cilician foothills, and her brood is already ranging into the livestock paths. Patrols are gone. Whole family groups vanished. The nest is active and deepening, and if it is not ended in the lair, her children will be in the coastal cities before the next dark moon. Apollo will not enter the nest. The oracle says mortals must.
Melitta gives the party the Tripod Brand of Arima — ash-iron, quenched in the Pythia’s tripod, bearing a Delphic laurel stamp still warm to the touch. It bites Echidna’s summons and, pressed to the nest stone or her coil at the right moment, makes her forget a name she was about to speak. It has limited uses. The party will need to choose when to spend them. The outer brood is the door. Echidna is the room behind it. Phase Three will be the most dangerous thing in this session by design — that is not a warning; it is a promise.
Enc. 1 (Outer Brood): Brand (1/SR): disadvantage on one brood-beast’s attacks vs. brand-wielder. Non-combat path: offer meat/wine + Animal Handling/Persuasion group check (3 successes before 3 failures, DC 14) to draw Death Dogs off while the party reaches the chimney — still face 1 Dracaena at the lip (or bribe her with 50+ gp). Kimon is worth saving: Medicine DC 12 or any healing frees him; in Enc. 2 he can ignore bone-scree difficult terrain once, or point out a ½-cover ledge. Dracaena mercy (Persuasion DC 15 on downed enemy): she hisses a warning about Phase 2’s Orthrus, then flees.
Enc. 2 Phase 1–2 (Hard): Brand: cancel one Call Brood per phase (or dismiss one CR ≤5 summon). Tell Orthrus from Cerberus clearly — two heads only. Phase 2 free Call on transition: summon Orthrus or Brood Sphinx. Lair actions: Bone Scree, Nest Gasp (Phase 1); Coil Quake unlocked Phase 2+. Keep summoned turns fast — use average damage.
Enc. 2 Phase 3 (Deadly): Phase 3 transition roar — each enemy Wis DC 16 or frightened. Free Call Brood: Lernean Brood-Hydra (preferred) or Chimera+Orthrus. Brand finale: 1 round no Call Brood + disadvantage on Constrict. Hydra with 3 heads if full 5-head risks unfair TPK. Win: Echidna 0 HP; remaining summons flee into tunnels.
Key NPCs
Melitta of Delphi
Melitta · Quest Giver · Neutral — Oracle’s courier from Delphi, traveling in the plain gray robe of a temple runner. She has delivered six commissions like this in the last year, all of them requests Apollo cannot fulfill directly, and she has learned to lead with the Brand rather than the explanation. She carries the pythia-ash packet sealed in clay — it will not open unless the party intends to use it — and she will not be in the party’s way once the delivery is made. Secret: Apollo genuinely cannot enter the nest. It is not a political limitation; Echidna predates the Olympian order and the nest-space is not inside Apollo’s authority. This worries Melitta more than she shows, because it means a divine failure condition exists. RP Hook: Ask her why Delphi is involved. She will give the official answer first (the oracle named the threat). Ask a second time: she will admit that the Pythia wept when she gave the commission, which is unusual. The oracle has seen versions of this that did not go well. Insight DC 14: Melitta does not know the Brand has more range than she told them — she was only given the short version of the instructions.
Kimon the Goatherd-Scout
Kimon · Recruitable Ally · Neutral Good — Local goatherd, mid-thirties, extremely practical, currently pinned under a collapsed goat-pen in the Enc. 1 ravine with a dislocated shoulder and a clear line of sight to the chimney entrance. He lost his entire flock to the outer brood three nights ago and has been waiting here since, which means he has had an extended period to study the Death Dogs’ patrol pattern and the Dracaena’s shift-change timing. He is the best possible Enc. 2 navigator available and he costs the price of a successful Medicine DC 12. Secret: He once got into the chimney — the top section, at least — to retrieve a goat that had fallen in. The nest-smell drove him back but he saw the bone shelves and the pool. His description of the pool is accurate: black water, cold, a faint sound like a very large thing breathing. RP Hook: He will tell the party everything he knows without prompting; he is not difficult. The only complication is that his description of what is in the nest is so calm and specific that it is more unsettling than a panicked account would be. Insight DC 10: he is not calm; he has been sitting with the knowledge long enough that calm is all that’s left.
Lair Setting — Arima
- Locale: Cilicia — cave mouth in a ravine → bone-chimney → gargantuan nest-cavern with black pool.
- Maps: Enc. 1 ravine ledge 60×40; Enc. 2 nest 100×80 with 20×20 pool, bone shelves, 40-ft ceiling.
- Summon ban: Echidna may call many children — not Typhon, not Cerberus. Orthrus (two-headed) is fine.
- Rest: Short Rest only between Enc. 1 and 2 (the nest wakes). No Long Rest inside.
Major Beats
- Melitta + Tripod Brand at the mist-line.
- Enc. 1: Outer Brood — death dogs, harpies, dracaena; recruit Kimon.
- Enc. 2: Multi-phase Echidna — Phase 1 Hard → Phase 2 Bard-Hard → Phase 3 Deadly.
- Victory: Mother slain / nest stills; brood scatters into myth.
Session Rewards
Keepable prizes earned by completing (or excelling at) this session. One character claims each reward unless noted. Full cards are under Reward Cards.
| Reward | Description | Criteria |
|---|---|---|
| Tripod Brand of Arima | Ash-iron brand that makes brood forget a name and spoils one call. | Endure Echidna's rising phases and leave the nest with the Delphic brand intact. |
Creature / Enemy List
| Creature | Easy | Med | Hard | 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 |
Encounter 1 — The Outer Brood
Overview
The ravine is a still life in bone. Two-headed Dogs patrol a rough triangle between the chimney entrance, the collapsed goat-pen, and a limestone overhang where a Brood Harpy roosts. The Dracaena Guard stands at the chimney lip with the quiet patience of something that has been told to stand there until it is killed or relieved and has no opinion about which happens first. The smell is ancient blood and cold stone. Below, from the chimney, a faint sound rises: very regular, very large breathing. Kimon is under the pen to the south-east, one shoulder wrong, watching everything with the deliberate calm of a man who ran out of panic days ago.
3× Death Dogs + 2× Brood Harpies + 1× Dracaena Guard. Kimon is pinned under the collapsed goat-pen (½ cover) — free him (Medicine DC 12 or any healing) to gain Enc. 2 Guide and Warning Cry.
Encounter Roster (Hard)
- 3× Death Dog (CR 1 · 200 XP each)
- 2× Brood Harpy (CR 1 · 200 XP each)
- 1× Dracaena Guard (CR 3 · 700 XP)
XP / Notes
- 3×200 + 2×200 + 700 = 1,700 XP (gateway fight)
- Non-combat path reduces XP pressure by design — resource conservation for Enc. 2 is the point
- Short Rest only at chimney mouth after fight (something huge exhales below)
🗺 Terrain & Features
60×40 ravine · chimney entrance north (climb Ath DC 12 down 40 ft. after fight) · scree difficult terrain in two 10-ft patches · collapsed goat-pen (SE, ½ cover for Kimon) · limestone overhang west (Harpy roost, half cover; dislodging: Str DC 12) · brand: disadvantage on one brood-beast attack vs. brand-wielder (1/SR).
Mechanics
- 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.
Creature Cards
Death Dog (Two-Headed Brood)
Medium Monstrosity, Neutral Evil · CR 1 · Mini-optional
AC 12 | HP 39 | Speed 40 ft.
Two heads: adv on Perception · Sleep / charm: save once for both heads
Not Cerberus. Two-headed only — never stage as Cerberus.
Multiattack. Two bites.
Bite. +4 to hit. Hit: 5 (1d6+2) piercing + Con DC 12 or poisoned; fail by 5+ also diseased (HP max −3 until cured).
Brood Harpy
Medium Monstrosity, Chaotic Evil · CR 1
AC 11 | HP 38 | Speed 20 ft., fly 40 ft.
Nest scouts of the outer chimney
Claws. +3 to hit. Hit: 6 (2d4+1) slashing.
Luring Song. 300 ft.; Wis DC 11 or charmed + incapacitated, move toward harpy. Ends if damaged / deafened.
Dracaena Guard
Large Monstrosity, Neutral Evil · CR 3 · Echidna’s door-wardens
AC 14 | HP 68 | Speed 30 ft.
Woman-serpent hybrids; speak broken Common
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.
Multiattack. Spear and constrict.
Spear. +5 to hit. Hit: 8 (1d8+3) piercing.
Constrict. +5 to hit. Hit: 10 (2d6+3) bludgeoning + grapple (escape DC 13).
Kimon the Goatherd-Scout
Medium Humanoid, Neutral Good · CR 1/2 · Recruitable
AC 12 | HP 18 | Speed 30 ft.
Lost his flock to the Outer Brood; knows a side-chimney into Enc. 2
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.
Sling. +4 to hit, range 30/120. Hit: 4 (1d4+2) bludgeoning.
Warning Cry. Bonus action: one ally within 30 ft. not surprised by a Call Brood arrival this round.
Tripod Brand of Arima
Wondrous Item (maguffin), Unique
Appearance: iron brand, ash-black, warm; Delphic laurel stamp
Handout (22 words). "When the Mother calls her children from the dark, press this ash-iron to the stone — the nest forgets one name."
Enc. 1. Action (1/short rest): brand a brood-beast within 5 ft. — it has disadvantage on attacks vs. you until end of its next turn.
Enc. 2 payoff. Action once per phase: press to nest stone / Echidna’s coil. Cancel her next Call Brood (or dismiss one summoned creature of CR 5 or less as it arrives). Phase 3: instead, for 1 round Echidna cannot use Call Brood and has disadvantage on Constrict.
Encounter 2 — Mother of the Deep Coil (Multi-Phase)
Overview
The chimney opens into a cavern that smells of old water and something older. The pool is exactly as Kimon described: black, cold, a surface so still it could be stone until it is not. Echidna is already visible — half in the water, half on the bone shelf north of the pool, coiled with the patience of something that has been here since before the gods named it. She sees the party before they see all of her. Her eyes are amber and deliberate. She does not look like a monster interrupted — she looks like a host receiving guests she expected earlier and has been keeping a meal warm for.
Three phases as HP falls. Each phase transition: free immediate action. Phase 3 is Deadly by design. The Brand is the party’s primary leverage per phase — three uses, three phases, no waste. Budget Enc. 2 as the session’s main dish; Enc. 1 was the warm-up and the resource-drain.
Phase Summary
- Phase 1 (HP 310–207): Hard · full Multiattack · Call Brood R5-6
- Phase 2 (HP 206–104): Hard+ · free Orthrus on transition · Coil Quake lair
- Phase 3 (HP 103–0): Deadly · Wis DC 16 frighten roar · Hydra summon · +2 to hit · Call legendary (cost 3)
XP Budget
- Echidna CR 14 = 11,500 XP + summons escalate per phase
- Phase 3 effective Deadly: ~22,800+ XP with active summons
- Hydra (CR 8) = 3,900 XP; Chimera (CR 6) = 2,300 XP
🗺 Terrain & Features
100×80 cavern · central pool 20×20 (deep; Drag Under to here = underwater hold-breath rules) · bone shelves north and east (½ cover, climb DC 10; Bone Scree lair action makes them difficult terrain) · two nest tunnels west and south (summon entry points; blocking a tunnel: Str DC 16 or wall of force / stone) · 40-ft ceiling (flying creatures can move freely; harpies/chimera favor this) · Echidna’s 20×20 space: difficult terrain to move through (Constrict OA once per turn).
Phase Rules
Phase 1 — Coil and Call (HP 310–207) · Hard
- 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.
Phase 2 — Children of the Nest (HP 206–104) · Hard+
- 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).
Phase 3 — Blood-Mother Ascendant (HP 103–0) · DEADLY
- 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.
- Echidna gains +2 to hit; Bite poison DC 19; Call Brood legendary (cost 3) available.
- Max summons raised; Hydra counts as 2 toward cap.
- Brand finale: 1 round — no Call Brood + disadv on Constrict (once).
- Win: Echidna 0 HP. Remaining summons flee into tunnels (chase optional, not required).
DM Pacing Notes
- Keep summoned turns fast — telegraph attacks, use average damage if slow.
- If Phase 3 will TPK unfairly due to dice: have Hydra arrive with 3 heads instead of 5, or delay legendary Call once.
- Still no Typhon cameo. Still no Cerberus.
Creature Cards
Echidna, Mother of Monsters
Gargantuan Monstrosity, Chaotic Evil · CR 14 (phases escalate to Deadly) · BOSS
AC 17 (natural) | HP 310 (20d20+100) | Speed 40 ft., burrow 20 ft., swim 40 ft.
Saves: Dex +7, Con +10, Wis +8 · Resist: poison, BPS nonmagical · Immune: poisoned · Senses: darkvision 120 ft. · LR 3/day
Gargantuan Coil. Space 20×20 ft. (tail sweeps further). Occupies nest pool + shore. PCs can move through her space as difficult terrain (she may Constrict as OA once per turn).
Mother’s Call. See phase rules — she summons brood. Never Typhon. Never Cerberus. Prefer Orthrus, Chimera, lesser Hydra, Sphinx, Death Dogs, Harpies, Dracaenae.
Phase Thresholds. Phase 1: HP 310–207. Phase 2: 206–104. Phase 3 (Deadly): 103–0 — Blood-Mother Ascendant.
Persistence. Defeating her (0 HP) ends the threat of this awakening. She is a monster-mother, not a god — world remains intact. Typhon is absent (elsewhere / sealed); do not introduce him.
Multiattack. One Bite and one Constrict, or two Tail Sweeps.
Bite. +12 to hit, reach 15 ft. Hit: 20 (3d8+7) piercing + 14 (4d6) poison (Con DC 18 or poisoned 1 minute).
Constrict. +12 to hit, reach 10 ft. Hit: 21 (4d6+7) bludgeoning + grapple (escape DC 20). Until grapple ends, target is restrained; Echidna can’t constrict another.
Tail Sweep. +12 to hit, reach 20 ft. Hit: 16 (2d8+7) bludgeoning; Str DC 20 or prone.
Call Brood (Recharge 5–6). Summon brood per current phase (see encounter). Arrives in unoccupied spaces within 60 ft. Max summoned creatures at once: Phase 1 = 3, Phase 2 = 4, Phase 3 = 5 (Hydra counts as 2).
Venom Spew (Recharge 5–6). 30-ft cone Dex DC 18; 28 (8d6) poison; failure also blinded until end of next turn.
Drag Under. Move a constricted creature 15 ft. toward nest pool; if pool entered, creature is underwater (hold breath rules).
Detect (1). Wis (Perception) check.
Tail (1). One Tail Sweep.
Hiss (2). One creature within 60 ft. Wis DC 18 or frightened until end of its next turn.
Call (3, Phase 3 only). Use Call Brood even if not recharged; then Call Brood recharges on 6 only until she finishes a long rest.
Bone Scree. Difficult terrain in a 20-ft radius until next init 20.
Nest Gasp. Poison fog lightly obscures a 30-ft cube for 1 round; entering/starting there Con DC 15 or 7 (2d6) poison.
Coil Quake (Phase 2+). Each creature on ground within 30 ft. Dex DC 15 or prone.
Tripod Brand of Arima
Wondrous Item (maguffin), Unique
Appearance: iron brand, ash-black, warm; Delphic laurel stamp
Handout (22 words). "When the Mother calls her children from the dark, press this ash-iron to the stone — the nest forgets one name."
Enc. 1. Action (1/short rest): brand a brood-beast within 5 ft. — it has disadvantage on attacks vs. you until end of its next turn.
Enc. 2 payoff. Action once per phase: press to nest stone / Echidna’s coil. Cancel her next Call Brood (or dismiss one summoned creature of CR 5 or less as it arrives). Phase 3: instead, for 1 round Echidna cannot use Call Brood and has disadvantage on Constrict.
Orthrus
Large Monstrosity, Neutral Evil · CR 5 · Two-headed hound · NOT Cerberus
AC 14 | HP 85 | Speed 50 ft.
Brother of Cerberus in myth — do not replace with Cerberus. Two heads only.
Pack Howl. Allied brood within 30 ft. have advantage on melee attacks vs. a creature Orthrus has bitten this turn.
Multiattack. Two bites.
Bite. +7 to hit. Hit: 11 (2d6+4) piercing + Con DC 14 or poisoned 1 minute.
Double Maw (Recharge 5–6). One bite at +7 with advantage; Hit: 18 (4d6+4) piercing and knock prone.
Chimera
Large Monstrosity, Chaotic Evil · CR 6 · Classic brood-child
AC 14 | HP 114 | Speed 30 ft., fly 60 ft.
Lion / goat / dragon heads
Multiattack. Bite, horns, and claws.
Bite. +7. Hit: 11 (2d6+4) piercing.
Horns. +7. Hit: 10 (1d12+4) bludgeoning.
Claws. +7. Hit: 11 (2d6+4) slashing.
Fire Breath (Recharge 5–6). 15-ft cone Dex DC 15; 31 (7d8) fire.
Lernean Brood-Hydra (Lesser)
Huge Monstrosity, Unaligned · CR 8 · Staged lesser hydra · Phase 3 summon
AC 15 | HP 150 (heads matter more) | Speed 30 ft., swim 30 ft.
Starts with 5 heads. Not immortal regeneration — simplified for Deadly pace.
Multiple Heads. 5 heads. While it has >1 head, adv on saves vs. blind/deaf/stun/charm. Loses 30 HP → lose 1 head (and one bite from Multiattack). At 0 heads, dies.
Reactive Heads. 1 reaction per head for opportunity attacks.
Multiattack. As many bite attacks as it has heads (max 5).
Bite. +8 to hit, reach 10 ft. Hit: 10 (1d10+5) piercing.
Brood Sphinx (Winged Riddler)
Large Monstrosity, Lawful Evil · CR 5 · Optional Phase 2 alternate
AC 15 | HP 102 | Speed 40 ft., fly 60 ft.
Spell DC 14 — minor illusion, detect magic; Roar once
Multiattack. Two claws; may replace one with Roar if available.
Claw. +7. Hit: 11 (2d6+4) slashing.
Roar (1/day). Each creature of its choice within 60 ft. Wis DC 14 or frightened 1 minute.
⚖️ Difficulty Scaling
As Written ★ — 6 Players, Average Level 12
- Baseline for this guide. Encounter 1–2 are Hard; the final encounter is Deadly for six PCs at average level 12.
- XP budgets (6×L12 thresholds): Hard ≈ 14,400 · Deadly ≈ 22,800. Prefer mythic pressure, lair actions, and elite packs over endless CR1 swarms.
Library Standard — 6 Players, Average Level 8
- Major dial-back: reduce boss HP ~35–40%; strip one legendary action and one recharge; Favor/track thresholds −2 where present; skill DCs −2; cut one full minion wave from each fight.
Easier (table still high-tier)
- APL 10–11: boss HP −15%; remove one legendary; final Deadly → Hard by cutting one elite.
Harder
- APL 13–14 or seven PCs: boss HP +15%; +1 legendary; add one lair pulse or elite reinforcement mid-finale.
📋 Appendix — Cards
Quest / Item / Ally
Melitta of Delphi (Quest Giver)
Medium Humanoid, Neutral · Oracle’s courier
Mist → Cilician foothills; carries sealed pythia-ash
Motivation. Livestock, heroes, and whole patrols vanish into Arima’s deep. The Pythia names the Mother of Monsters awake in her own coil — she must be defeated in her lair before her brood spills into the plains.
Secret. Apollo will not enter the nest. Mortals must. The brand she gives was quenched in the Pythia’s tripod — it bites Echidna’s summons.
Override note. This session is 2 encounters; Enc. 2 is a long multi-phase fight. Phase 3 is Deadly by design (user override of the usual Hard-cap).
Tripod Brand of Arima
Wondrous Item (maguffin), Unique
Appearance: iron brand, ash-black, warm; Delphic laurel stamp
Handout (22 words). "When the Mother calls her children from the dark, press this ash-iron to the stone — the nest forgets one name."
Enc. 1. Action (1/short rest): brand a brood-beast within 5 ft. — it has disadvantage on attacks vs. you until end of its next turn.
Enc. 2 payoff. Action once per phase: press to nest stone / Echidna’s coil. Cancel her next Call Brood (or dismiss one summoned creature of CR 5 or less as it arrives). Phase 3: instead, for 1 round Echidna cannot use Call Brood and has disadvantage on Constrict.
Kimon the Goatherd-Scout
Medium Humanoid, Neutral Good · CR 1/2 · Recruitable
AC 12 | HP 18 | Speed 30 ft.
Lost his flock to the Outer Brood; knows a side-chimney into Enc. 2
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.
Sling. +4 to hit, range 30/120. Hit: 4 (1d4+2) bludgeoning.
Warning Cry. Bonus action: one ally within 30 ft. not surprised by a Call Brood arrival this round.
Boss
Echidna, Mother of Monsters
Gargantuan Monstrosity, Chaotic Evil · CR 14 (phases escalate to Deadly) · BOSS
AC 17 (natural) | HP 310 (20d20+100) | Speed 40 ft., burrow 20 ft., swim 40 ft.
Saves: Dex +7, Con +10, Wis +8 · Resist: poison, BPS nonmagical · Immune: poisoned · Senses: darkvision 120 ft. · LR 3/day
Gargantuan Coil. Space 20×20 ft. (tail sweeps further). Occupies nest pool + shore. PCs can move through her space as difficult terrain (she may Constrict as OA once per turn).
Mother’s Call. See phase rules — she summons brood. Never Typhon. Never Cerberus. Prefer Orthrus, Chimera, lesser Hydra, Sphinx, Death Dogs, Harpies, Dracaenae.
Phase Thresholds. Phase 1: HP 310–207. Phase 2: 206–104. Phase 3 (Deadly): 103–0 — Blood-Mother Ascendant.
Persistence. Defeating her (0 HP) ends the threat of this awakening. She is a monster-mother, not a god — world remains intact. Typhon is absent (elsewhere / sealed); do not introduce him.
Multiattack. One Bite and one Constrict, or two Tail Sweeps.
Bite. +12 to hit, reach 15 ft. Hit: 20 (3d8+7) piercing + 14 (4d6) poison (Con DC 18 or poisoned 1 minute).
Constrict. +12 to hit, reach 10 ft. Hit: 21 (4d6+7) bludgeoning + grapple (escape DC 20). Until grapple ends, target is restrained; Echidna can’t constrict another.
Tail Sweep. +12 to hit, reach 20 ft. Hit: 16 (2d8+7) bludgeoning; Str DC 20 or prone.
Call Brood (Recharge 5–6). Summon brood per current phase (see encounter). Arrives in unoccupied spaces within 60 ft. Max summoned creatures at once: Phase 1 = 3, Phase 2 = 4, Phase 3 = 5 (Hydra counts as 2).
Venom Spew (Recharge 5–6). 30-ft cone Dex DC 18; 28 (8d6) poison; failure also blinded until end of next turn.
Drag Under. Move a constricted creature 15 ft. toward nest pool; if pool entered, creature is underwater (hold breath rules).
Detect (1). Wis (Perception) check.
Tail (1). One Tail Sweep.
Hiss (2). One creature within 60 ft. Wis DC 18 or frightened until end of its next turn.
Call (3, Phase 3 only). Use Call Brood even if not recharged; then Call Brood recharges on 6 only until she finishes a long rest.
Bone Scree. Difficult terrain in a 20-ft radius until next init 20.
Nest Gasp. Poison fog lightly obscures a 30-ft cube for 1 round; entering/starting there Con DC 15 or 7 (2d6) poison.
Coil Quake (Phase 2+). Each creature on ground within 30 ft. Dex DC 15 or prone.
Outer Brood & Summons
Death Dog (Two-Headed Brood)
Medium Monstrosity, Neutral Evil · CR 1 · Mini-optional
AC 12 | HP 39 | Speed 40 ft.
Two heads: adv on Perception · Sleep / charm: save once for both heads
Not Cerberus. Two-headed only — never stage as Cerberus.
Multiattack. Two bites.
Bite. +4 to hit. Hit: 5 (1d6+2) piercing + Con DC 12 or poisoned; fail by 5+ also diseased (HP max −3 until cured).
Brood Harpy
Medium Monstrosity, Chaotic Evil · CR 1
AC 11 | HP 38 | Speed 20 ft., fly 40 ft.
Nest scouts of the outer chimney
Claws. +3 to hit. Hit: 6 (2d4+1) slashing.
Luring Song. 300 ft.; Wis DC 11 or charmed + incapacitated, move toward harpy. Ends if damaged / deafened.
Dracaena Guard
Large Monstrosity, Neutral Evil · CR 3 · Echidna’s door-wardens
AC 14 | HP 68 | Speed 30 ft.
Woman-serpent hybrids; speak broken Common
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.
Multiattack. Spear and constrict.
Spear. +5 to hit. Hit: 8 (1d8+3) piercing.
Constrict. +5 to hit. Hit: 10 (2d6+3) bludgeoning + grapple (escape DC 13).
Orthrus
Large Monstrosity, Neutral Evil · CR 5 · Two-headed hound · NOT Cerberus
AC 14 | HP 85 | Speed 50 ft.
Brother of Cerberus in myth — do not replace with Cerberus. Two heads only.
Pack Howl. Allied brood within 30 ft. have advantage on melee attacks vs. a creature Orthrus has bitten this turn.
Multiattack. Two bites.
Bite. +7 to hit. Hit: 11 (2d6+4) piercing + Con DC 14 or poisoned 1 minute.
Double Maw (Recharge 5–6). One bite at +7 with advantage; Hit: 18 (4d6+4) piercing and knock prone.
Chimera
Large Monstrosity, Chaotic Evil · CR 6 · Classic brood-child
AC 14 | HP 114 | Speed 30 ft., fly 60 ft.
Lion / goat / dragon heads
Multiattack. Bite, horns, and claws.
Bite. +7. Hit: 11 (2d6+4) piercing.
Horns. +7. Hit: 10 (1d12+4) bludgeoning.
Claws. +7. Hit: 11 (2d6+4) slashing.
Fire Breath (Recharge 5–6). 15-ft cone Dex DC 15; 31 (7d8) fire.
Lernean Brood-Hydra (Lesser)
Huge Monstrosity, Unaligned · CR 8 · Staged lesser hydra · Phase 3 summon
AC 15 | HP 150 (heads matter more) | Speed 30 ft., swim 30 ft.
Starts with 5 heads. Not immortal regeneration — simplified for Deadly pace.
Multiple Heads. 5 heads. While it has >1 head, adv on saves vs. blind/deaf/stun/charm. Loses 30 HP → lose 1 head (and one bite from Multiattack). At 0 heads, dies.
Reactive Heads. 1 reaction per head for opportunity attacks.
Multiattack. As many bite attacks as it has heads (max 5).
Bite. +8 to hit, reach 10 ft. Hit: 10 (1d10+5) piercing.
Brood Sphinx (Winged Riddler)
Large Monstrosity, Lawful Evil · CR 5 · Optional Phase 2 alternate
AC 15 | HP 102 | Speed 40 ft., fly 60 ft.
Spell DC 14 — minor illusion, detect magic; Roar once
Multiattack. Two claws; may replace one with Roar if available.
Claw. +7. Hit: 11 (2d6+4) slashing.
Roar (1/day). Each creature of its choice within 60 ft. Wis DC 14 or frightened 1 minute.
Reward Cards
Post-session keepables. Reward is the first tag. Mechanics below are for ongoing use after this oneshot.
Tripod Brand of Arima
Reward · Wondrous · 1/Short Rest
Mechanics. Once per short rest, as an action, brand a beast or monstrosity within 5 feet: it has disadvantage on attack rolls against you until the end of its next turn. Once per long rest, as an action, press the brand to stone or coil within 5 feet: cancel one creature's attempt to summon or call reinforcements this round, or dismiss one summoned creature of CR 5 or lower as it arrives (no save).
Appearance. An ash-black iron brand warm to the touch, face stamped with a Delphic laurel.
Lore. Arima's nest-forgetfulness, carried out after the Mother of Monsters was denied one child's name.
Quote. "When the Mother calls her children from the dark, press this ash-iron to the stone." — Tripod Brand
Earn when: Endure Echidna's rising phases and leave the nest with the Delphic brand intact.