Stymphalian Storm
For 6 level 8 PCs, 3 to 3.5 hours, 3 encounters. Enc. 3 is Hard.
📜 Session Summary
| Style Heroic lake-clearing hunt with noisy tools, risky improvisation, and a final airborne brawl. |
| Win Condition The flock breaks, the lake reopens, and the last bronze feathers are claimed before they seed a wider plague. |
| Loss Condition The birds scatter into farms and roads; the lake survives, but every nearby roof and field becomes a target. |
| Players 6 × Level 8 · 3–3.5 hrs · 3 encounters |
| Key Ally Itys of the Whistling Reeds (recruit Enc. Enc. 1 or Enc. 2) · Maguffin: Thunder-Net of Stymphalos |
Description
Alkippe Reed-Warden hooks the party. Maguffin Thunder-Net of Stymphalos pays off in the finale against Storm Matriarch. Recruit Itys of the Whistling Reeds along the way.
Clear a lake of bronze-beaked birds using thunder, nets, and bad ideas.
Major Beats
- A bronze feather punches through a shield like a thrown spear.
- Villagers argue for fire while children hide under reed mats.
- Thunder answers at exactly the wrong moment.
- The matriarch's shadow turns the whole lake black.
Creature / Enemy List
| Creature | Easy | Med | Hard | Notes |
|---|---|---|---|---|
| Bronze-Beaked Stymphalian | — | med | hard | CR 3 · Fast skirmisher |
| Razor-Feather Flock | — | med | hard | CR 5 · Area denial swarm |
| Nest Sentinel of Ares | — | med | hard | CR 6 · Armored bruiser |
| Storm Matriarch | — | med | hard | CR 9 · Boss, aerial controller |
| Itys of the Whistling Reeds | — | 1 | 1 | Recruit Enc. Enc. 1 or Enc. 2 |
Encounter 1 — Reeds Under Siege
Overview
Evacuate fishers, learn why the flock returned, and choose bait, thunder, or stealth for the hunt.
🗺 Terrain
Flooded village docks, reed huts, half-sunk skiffs, and a bell tower full of bronze scratches.
Mechanics
- Run a 4-success DC 15 group challenge using Nature, Survival, Athletics, Persuasion, or Animal Handling.
- Every failure costs a skiff, a cache of nets, or 10 HP split among exposed villagers.
- Finding the stolen Ares-bronze grants advantage on one Enc. 2 lure or bait check.
- Recruit Itys by saving his skiff or accepting his reed-maze shortcut despite Alkippe's anger.
Creature Cards
Alkippe Reed-Warden
Human lake reeve, exhausted civic hunter
Motivation. Reopen the lake before hunger and panic make the townsfolk burn the marsh.
Secret. Her brother looted Ares-bronze from the shore and drew the flock back with it.
Hard rule. She will not allow the party to poison the lake or torch nesting reeds with families hiding nearby.
Thunder-Net of Stymphalos
Storm-charged hunting net, single-use mythic snare
Appearance: A tarred hemp net threaded with blue wire and small bronze bells.
Handout. "Throw only when the sky answers. Pull only if you like keeping both arms."
Enc. 1–2. Can capture a scout bird, block a dangerous dive lane, or grant advantage on one flock-control check.
Enc. 3. If spread across the nest spire during thunder, grounds the boss for 2 rounds and strips its reaction.
Itys of the Whistling Reeds
Medium Humanoid, Neutral · Recruitable Ally · Local net-runner and bird-call mimic
AC 15 | HP 58 | Speed 30 ft.
Role: Local net-runner and bird-call mimic
RECRUITMENT (Enc. Enc. 1 or Enc. 2). Save his skiff, forgive his theft of bronze bait, or let him lead the reed-maze route.
Aid. Acts on party initiative when recruited; prefers nonlethal when asked.
Strike. Reed spear +6 to hit, 7 piercing; once per fight, mimic call imposes disadvantage on one bird dive.
Bronze-Beaked Stymphalian
Medium Creature · CR 3 · Fast skirmisher
AC 15 | HP 45 | Speed 30 ft.
Note. Use in pairs or as minion flights during dives.
Attack. Bronze beak +6 to hit, 10 piercing; flyby avoids opportunity attacks.
Encounter 2 — Thunder, Nets, and Bad Ideas
Overview
Cross the lake under aerial harassment while setting a storm lure before the flock can scatter.
🗺 Terrain
Open gray water, reed blinds, three lure rafts, and a lightning-struck standing stone.
Mechanics
- Need 5 successes before 3 failures at DC 16 to herd the flock toward the rookery.
- Good bad ideas count: drums, reflected sunlight, tied shields, spell thunder, or fake carrion.
- On a failure, a Razor-Feather Flock attacks for 2 rounds or destroys one prepared lure.
- Spending the Thunder-Net here prevents the easiest Enc. 3 payoff but removes one enemy from the finale.
Creature Cards
Thunder-Net of Stymphalos
Storm-charged hunting net, single-use mythic snare
Appearance: A tarred hemp net threaded with blue wire and small bronze bells.
Handout. "Throw only when the sky answers. Pull only if you like keeping both arms."
Enc. 1–2. Can capture a scout bird, block a dangerous dive lane, or grant advantage on one flock-control check.
Enc. 3. If spread across the nest spire during thunder, grounds the boss for 2 rounds and strips its reaction.
Itys of the Whistling Reeds
Medium Humanoid, Neutral · Recruitable Ally · Local net-runner and bird-call mimic
AC 15 | HP 58 | Speed 30 ft.
Role: Local net-runner and bird-call mimic
RECRUITMENT (Enc. Enc. 1 or Enc. 2). Save his skiff, forgive his theft of bronze bait, or let him lead the reed-maze route.
Aid. Acts on party initiative when recruited; prefers nonlethal when asked.
Strike. Reed spear +6 to hit, 7 piercing; once per fight, mimic call imposes disadvantage on one bird dive.
Razor-Feather Flock
Medium Creature · CR 5 · Area denial swarm
AC 14 | HP 92 | Speed 30 ft.
Note. Disperses for 1 round if hit by thunder damage.
Attack. Feather storm, DC 15 Dexterity save or 21 slashing in a 20-foot burst.
Nest Sentinel of Ares
Medium Creature · CR 6 · Armored bruiser
AC 17 | HP 110 | Speed 30 ft.
Note. Guards eggs and stolen bronze rather than fighting to the death.
Attack. Two talon strikes +7 to hit, 12 slashing each; shriek frightens on DC 15 Wisdom.
Encounter 3 — The Bronze Rookery
Overview
Fight across a rocking nest-island as the matriarch calls lightning and tries to launch the rookery skyward.
🗺 Terrain
Bone-white island, thorny nest spire, waist-high water, three egg mounds, and storm clouds overhead.
Mechanics
- At initiative 20, wind shifts: DC 15 Strength or Dexterity save or slide 10 feet toward water or spikes.
- Egg mounds are hazards; destroying them ends adds but worsens Alkippe's settlement politics.
- Maguffin payoff: anchor the Thunder-Net during thunder to ground the boss for 2 rounds.
- If the boss falls below 35 HP, a successful DC 16 Intimidation or Animal Handling check can break the flock without slaughter.
Creature Cards
Thunder-Net of Stymphalos
Storm-charged hunting net, single-use mythic snare
Appearance: A tarred hemp net threaded with blue wire and small bronze bells.
Handout. "Throw only when the sky answers. Pull only if you like keeping both arms."
Enc. 1–2. Can capture a scout bird, block a dangerous dive lane, or grant advantage on one flock-control check.
Enc. 3. If spread across the nest spire during thunder, grounds the boss for 2 rounds and strips its reaction.
Bronze-Beaked Stymphalian
Medium Creature · CR 3 · Fast skirmisher
AC 15 | HP 45 | Speed 30 ft.
Note. Use in pairs or as minion flights during dives.
Attack. Bronze beak +6 to hit, 10 piercing; flyby avoids opportunity attacks.
Nest Sentinel of Ares
Medium Creature · CR 6 · Armored bruiser
AC 17 | HP 110 | Speed 30 ft.
Note. Guards eggs and stolen bronze rather than fighting to the death.
Attack. Two talon strikes +7 to hit, 12 slashing each; shriek frightens on DC 15 Wisdom.
Storm Matriarch
Large Creature · CR 9 · Boss, aerial controller · Boss
AC 18 | HP 168 | Speed 40 ft.
Role: Boss, aerial controller
Note. Boss last. Bloodied at half HP, she tries to lift the whole nest into the storm.
Hard encounter focus. Win condition may be steal, escape, disable, or drive-off — not always kill.
Multiattack / Assault. Multiattack with beak and two wings; lightning screech recharges on 5-6 for 36 lightning/thunder.
Advance (1). Move up to half Speed.
Strike (1). One attack from Assault.
⚖️ Difficulty Scaling
As Written ★ — 6 Players, Average Level 8
- Baseline for this guide. Numbers, DCs, and win tracks assume six PCs at average level 8.
Library Standard — 6 Players, Average Level 8
- Identical to As Written — this guide’s baseline is already 6 PCs at average level 8.
Easier
- APL 4–6: reduce minion counts ~30%; DCs −2; boss loses one recharge or legendary option.
Harder
- APL 10–12: boss HP +25–35%; +1 legendary action; add a lieutenant or extra wave.
📋 Appendix — Cards
Alkippe Reed-Warden
Human lake reeve, exhausted civic hunter
Motivation. Reopen the lake before hunger and panic make the townsfolk burn the marsh.
Secret. Her brother looted Ares-bronze from the shore and drew the flock back with it.
Hard rule. She will not allow the party to poison the lake or torch nesting reeds with families hiding nearby.
Thunder-Net of Stymphalos
Storm-charged hunting net, single-use mythic snare
Appearance: A tarred hemp net threaded with blue wire and small bronze bells.
Handout. "Throw only when the sky answers. Pull only if you like keeping both arms."
Enc. 1–2. Can capture a scout bird, block a dangerous dive lane, or grant advantage on one flock-control check.
Enc. 3. If spread across the nest spire during thunder, grounds the boss for 2 rounds and strips its reaction.
Itys of the Whistling Reeds
Medium Humanoid, Neutral · Recruitable Ally · Local net-runner and bird-call mimic
AC 15 | HP 58 | Speed 30 ft.
Role: Local net-runner and bird-call mimic
RECRUITMENT (Enc. Enc. 1 or Enc. 2). Save his skiff, forgive his theft of bronze bait, or let him lead the reed-maze route.
Aid. Acts on party initiative when recruited; prefers nonlethal when asked.
Strike. Reed spear +6 to hit, 7 piercing; once per fight, mimic call imposes disadvantage on one bird dive.
Bronze-Beaked Stymphalian
Medium Creature · CR 3 · Fast skirmisher
AC 15 | HP 45 | Speed 30 ft.
Note. Use in pairs or as minion flights during dives.
Attack. Bronze beak +6 to hit, 10 piercing; flyby avoids opportunity attacks.
Razor-Feather Flock
Medium Creature · CR 5 · Area denial swarm
AC 14 | HP 92 | Speed 30 ft.
Note. Disperses for 1 round if hit by thunder damage.
Attack. Feather storm, DC 15 Dexterity save or 21 slashing in a 20-foot burst.
Nest Sentinel of Ares
Medium Creature · CR 6 · Armored bruiser
AC 17 | HP 110 | Speed 30 ft.
Note. Guards eggs and stolen bronze rather than fighting to the death.
Attack. Two talon strikes +7 to hit, 12 slashing each; shriek frightens on DC 15 Wisdom.
Storm Matriarch
Large Creature · CR 9 · Boss, aerial controller · Boss
AC 18 | HP 168 | Speed 40 ft.
Role: Boss, aerial controller
Note. Boss last. Bloodied at half HP, she tries to lift the whole nest into the storm.
Hard encounter focus. Win condition may be steal, escape, disable, or drive-off — not always kill.
Multiattack / Assault. Multiattack with beak and two wings; lightning screech recharges on 5-6 for 36 lightning/thunder.
Advance (1). Move up to half Speed.
Strike (1). One attack from Assault.