The Atlantean Toll
One-Shot · 6 Players · Level 10 · Trireme + Enemy Galley · Atlantean Boarding
📜 Session Summary
| Style Boarding Action — Elemental skirmish → Galley clash → Deep-beast boss |
| Win Break the false toll; defeat or drive off the Keto-Spawn |
| Players 6 × Level 10 · 3–3.5 hrs · Entirely shipboard · Enc. 1–2 Hard · Finale Deadly |
| Minis Sahuagin-as-Atlantean (≤4), Kuo-toa (≤4), Steam mephit (≤4), Triton caster, Tritons (≤4 on table), Deep-sea monster; 2nd ship: Atlantean galley |
| Setting Open sea — the Atlantean galley runs alongside the party trireme on a sunlit day that turns suddenly wrong; the false toll-collectors are well-organized, have legitimate-looking insignia, and the Keto-Spawn swimming beneath the hull is the guarantee they never have to explain themselves. |
| Atmosphere Maritime intimidation escalating to chaos — the session opens with procedural menace (steam, obscured visibility, the galley signal), sharpens into a boarding confrontation with a legitimate counter-argument (the Bronze Tithe-Token), and detonates with a deep-sea monster on the ram; the Wave-Caller's ambivalence is the moral center. |
| Materials Wet teak decking, the hiss of steam mephit deaths, bronze medallion still warm from a clerk's pocket, grapple hooks biting through the gunwale, the Keto-Spawn's bioluminescent lure-light visible through the hull planks before it surfaces. |
| Tone Confrontational and political with a monster-horror finale — the Atlanteans are not entirely wrong to demand a sea-toll, they are wrong to have no authorization for this specific toll; the Tithe-Token is both weapon and argument, and using it well should feel like winning a legal dispute with a sword still in your hand. |
Description
A Clerk of the Blue Tithe presses the Bronze Tithe-Token into the party's hands just before the Atlantean galley comes alongside — Poseidon's authentic seal, warm from the clerk's pocket. The galley's crew claims to collect the ancient sea-tax on the god's behalf. They have the insignia, the correct demand, and a deep-sea horror swimming beneath the hull as their enforcement guarantee. What they don't have is authorization — and the Bronze Tithe-Token will prove it, if the party can get someone on the other side to listen.
The session is three escalating phases of the same confrontation. Phase one (Enc. 1): steam mephits boil up through the oar-ports as the galley approaches — signaling the galley that the party trireme has stopped evasive maneuvers, generating fog cover for the grappling team. Phase two (Enc. 2): grappling hooks, boarding Atlanteans, and a Triton Wave-Caller who is genuinely uncertain whether the toll is legitimate — show him the token. Phase three (Enc. 3): the Keto-Spawn, which doesn't care about the politics at all, climbs the 15-ft ram onto the bow deck and makes this a monster problem regardless of what the paperwork says.
The Bronze Tithe-Token is simultaneously the evidence, the argument, and the weapon. Handout DM payoff: when the token is shown to the Wave-Caller in Enc. 2 and he stares at it before issuing a parley order, read the handout inscription. When the token is held up to the Keto-Spawn in Enc. 3 and the beast — which should not understand documents — hesitates, let that moment of cosmic bureaucracy land.
Trireme + Enemy Galley
Main deck 40×50 ft · raised bow +15 ft · raised stern +25 ft · 90 ft total length (tapered ends) · center mast/sail · 15 ft ram at bow. Board supports up to 2 additional ships. Place Atlantean galley (≈70×25 ft) starboard, 5–10 ft gap / grappled.
Major Beats & DM Notes
- Opening — The Clerk's Warning. The Clerk boards the trireme at dawn looking like a man who has run out of time. History DC 14: the Blue Tithe is real, but it's collected by Triton wardens at blessed marker-buoys, not by armed galleys. Perception DC 13 on the token: it hums faintly, resonating with salt water.
- Enc. 1 RP hook — The Steam Signal. The mephits are semaphoring "ship is complying" to the galley — not attacking, signaling. Insight DC 13 on the pattern. A PC who disrupts the signal (Religion DC 15 with token) causes the galley boarding crew to hesitate: −1 Atlantean from Enc. 2's starting roster.
- Enc. 2 RP hook — The Wave-Caller's Doubt. The Triton Wave-Caller was hired for theological legitimacy. Insight DC 14 on his face when the token appears: he's seen that stamp before, on real tithe stations. Persuasion DC 14 + token: parley pause. Religion DC 16 + token: he orders stand-down — becomes reluctant ally in Enc. 3 and reveals the Keto-Spawn's binding weakness.
- Enc. 3 RP hook — The Spawn Hesitates. Wave-Caller's dismissal command (if recruited, bonus action): Keto-Spawn Wis DC 14 save or loses action for 1 round. This is the burst window. Token presentation: Spawn treats holder as divine authority — won't use Consuming Bite on that PC until below 50% HP.
Roster
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 |
|---|---|---|
| Bronze Tithe-Token | Authentic sea-tax stamp that frightens false deep-collectors. | Authenticate Poseidon's true seal and turn back the deep-beast collecting for false kings. |
| Creature | E | M | H |
|---|---|---|---|
| Steam Mephit | 2 | 4 | 4 |
| Atlantean | 2 | 4 | 4+wave |
| Brine-Touched | 2 | 3 | 4 |
| Wave-Caller | — | 1 | 1 |
| Keto-Spawn | adj | 1 | 1 |
Encounter 1 — Steam on the Water
12× Steam Mephits boil up from the oar-ports as the Atlantean galley signals — denser fog, hotter bursts, and a coordinated semaphore that must be broken or the boarding wave arrives early. Win: clear mephits; spot the galley (Perception DC 14); optionally disrupt the steam-signal (Religion DC 15 with the token).
- Death bursts threaten sail (fire). Create Water / gust helps.
- Non-combat: Contests with buckets (Athletics DC 14 group) vent steam without full combat — success still counts as a Hard clear if the signal is broken.
- APL10 Hard pressure: mephits arrive in three waves of 4 (rounds 1, 2, and 4); if signal unbroken after round 3, Enc. 2 starts with +2 Atlanteans already grappled.
Steam Mephit
Small Elemental · CR 1/4 · Mini ×12 (waves of 4)
AC 11 | HP 26 | Speed 30 ft., fly 30 ft.
Death Burst: 5-ft steam Dex DC 12 or 7 (2d6) fire
Claws. +2 to hit. Hit: 2 (1d4) slashing + 2 fire.
Steam Breath (Recharge 5–6). 15-ft cone Dex DC 12; 7 (2d6) fire.
Encounter 2 — False Kings of the Wave
Grappling hooks. 6× Atlanteans + 4× Brine-Touched + 2× Triton Boarder (CR 2 elites) + Wave-Caller (hostile until Token shown).
- Non-combat: Brandish Tithe-Token + Religion/Persuasion DC 14 → Wave-Caller orders a parley pause; cultists may still attack.
- Combat: Blood Frenzy Atlanteans. Cut 3 grapple lines (AC 12/HP 8) to separate ships.
- RECRUIT: Token authenticity → Wave-Caller + 2 Triton Guards aid Enc. 3.
Atlantean Reaver (Sahuagin reskin)
Medium Humanoid, Lawful Evil · CR 1 · Mini: Sahuagin ×6
AC 14 | HP 32 (5d8+10) | Speed 30 ft., swim 40 ft.
Blood Frenzy: adv on melee vs. creatures that don’t have all HP
Limited minis. Only 4 figures — use waves off-board if needed, or elite the four.
Multiattack. Bite and spear — or two spears.
Bite. +5 to hit. Hit: 5 (1d4+3) piercing.
Spear. +5 to hit. Hit: 7 (1d8+3) piercing.
Brine-Touched Cultist (Kuo-toa reskin)
Medium Humanoid, Neutral Evil · CR 1 · Mini: Kuo-toa ×4
AC 14 | HP 36 (6d8+9) | Speed 30 ft., swim 30 ft.
Sticky shield; Otherworldly Perception (force/invisible awareness 30 ft)
Spear. +3 to hit. Hit: 4 (1d6+1).
Net. As merman net.
Slime Slap. +3 to hit. Hit: poisoned until end of next turn (DC 11 Con).
Triton Wave-Caller
Medium Humanoid (Triton), Neutral · CR 4 · Mini: Triton caster ×1
AC 14 | HP 65 (10d8+20) | Speed 30 ft., swim 30 ft.
Spell DC 13, +5 — fog cloud, gust of wind, tidal wave (1/day)
RECRUITMENT. If the party shows the Tithe-Token as authentic Poseidon seal (Religion DC 12), the Wave-Caller switches sides in Enc. 3.
Enemy default. Begins as Atlantean ally / hostage-priest on their galley.
Trident. +4 to hit. Hit: 5 (1d6+1).
Lightning Lure cantrip. +5, pull 10 ft, 1d8 lightning (scaled).
Encounter 3 — Keto-Spawn at the Ram (Boss)
Keto-Spawn climbs the 15 ft ram onto the bow deck. Optional: 2 remaining Atlanteans snipe from their galley.
- Win: Beast 0 HP or driven to flee at ≤25% HP if Tithe-Token branded successfully this fight.
- Bow deck = raised 15 ft zone; shoving it off (Str contest DC 15 while bloodied) deals 3d6 fall into its own thrash.
Keto-Spawn (Deep-Sea Monster)
Large Monstrosity, Neutral Evil · CR 10 · 5,900 XP · Mini: Deep-sea angler/shark hybrid
AC 17 | HP 220 (21d10+84) | Speed 25 ft., swim 50 ft.
Senses: blindsight 30 ft. (angler lure) · Resist: cold
Climb Hull. Treat ship walls as non-difficult; can end turn on main deck.
Lure Hypnosis. Start of turn: one creature within 30 ft. that can see the lure DC 16 Wis or frightened+move toward it.
Siege. Double damage to objects (oar banks, rail).
Multiattack. Bite and two claws.
Bite. +10 to hit. Hit: 22 (3d10+6) piercing; grapple escape DC 16.
Claw. +10. Hit: 15 (2d8+6) slashing.
Swallow (Recharge 5–6). Grappled Medium target DC 16 Str or swallowed — 4d6 acid/turn; escape 25 HP to cut out.
Detect (1). Perception check.
Claw (1). One claw.
Thrash (2). Each creature within 10 ft. Dex DC 16 or 17 (5d6) bludgeoning and prone.
Lure Pulse (3). One creature within 30 ft. Wis DC 16 or frightened until end of next turn and pulled 15 ft. toward Keto-Spawn.
Bronze Tithe-Token
Wondrous Item (maguffin)
Poseidon’s authentic tax seal
Handout (20 words). "Show the true bronze when false kings claim the wave — the deep-beast bows to the stamp, not the spear."
Enc. 2. Advantage on Intimidation/Persuasion vs Atlanteans once.
Enc. 3. Action, brandish at Deep-Beast within 30 ft.: DC 15 Wis save or frightened 1 min and cannot Climb Hull for 1 round (once).
⚖️ Difficulty Scaling
As Written ★ — 6 Players, Average Level 10
- Baseline for this guide. Encounter 1–2 are Hard; the final encounter is Deadly for six PCs at average level 10.
- XP budgets (6×L10): Hard ≈ 10,800 · Deadly ≈ 16,800. Prefer denser mephit waves, full boarding pressure, and a Deadly Keto-Spawn finale over endless CR1 spam.
Library Standard — 6 Players, Average Level 8
- Dial back: Enc. 1 uses 4 mephits only; Enc. 2 −2 Atlanteans; Keto-Spawn HP −20% and one fewer legendary; skill DCs −1.
Easier
- APL 8–9: use Library Standard, then remove the Enc. 2 reinforcement wave.
Harder
- APL 11–12: Keto-Spawn HP +20%; +1 legendary; Enc. 2 opens with grapples already set.
📋 Appendix
Atlantean Reaver (Sahuagin reskin)
Medium Humanoid, Lawful Evil · CR 1 · Mini: Sahuagin ×6
AC 14 | HP 32 (5d8+10) | Speed 30 ft., swim 40 ft.
Blood Frenzy: adv on melee vs. creatures that don’t have all HP
Limited minis. Only 4 figures — use waves off-board if needed, or elite the four.
Multiattack. Bite and spear — or two spears.
Bite. +5 to hit. Hit: 5 (1d4+3) piercing.
Spear. +5 to hit. Hit: 7 (1d8+3) piercing.
Brine-Touched Cultist (Kuo-toa reskin)
Medium Humanoid, Neutral Evil · CR 1 · Mini: Kuo-toa ×4
AC 14 | HP 36 (6d8+9) | Speed 30 ft., swim 30 ft.
Sticky shield; Otherworldly Perception (force/invisible awareness 30 ft)
Spear. +3 to hit. Hit: 4 (1d6+1).
Net. As merman net.
Slime Slap. +3 to hit. Hit: poisoned until end of next turn (DC 11 Con).
Steam Mephit
Small Elemental · CR 1/4 · Mini ×12 (waves of 4)
AC 11 | HP 26 | Speed 30 ft., fly 30 ft.
Death Burst: 5-ft steam Dex DC 12 or 7 (2d6) fire
Claws. +2 to hit. Hit: 2 (1d4) slashing + 2 fire.
Steam Breath (Recharge 5–6). 15-ft cone Dex DC 12; 7 (2d6) fire.
Triton Guard
Medium Humanoid (Triton), Neutral · CR 1 · Mini ×10 (use ≤4 here)
AC 13 | HP 27 | Speed 30/swim 30
Amphibious; Empathic Bond rumors
Optional allies. If Wave-Caller defects, 2 guards join (field from Triton ×10).
Spear. +4. Hit: 5 (1d6+2).
Conch Net. restrain DC 12.
Triton Wave-Caller
Medium Humanoid (Triton), Neutral · CR 4 · Mini: Triton caster ×1
AC 14 | HP 65 (10d8+20) | Speed 30 ft., swim 30 ft.
Spell DC 13, +5 — fog cloud, gust of wind, tidal wave (1/day)
RECRUITMENT. If the party shows the Tithe-Token as authentic Poseidon seal (Religion DC 12), the Wave-Caller switches sides in Enc. 3.
Enemy default. Begins as Atlantean ally / hostage-priest on their galley.
Trident. +4 to hit. Hit: 5 (1d6+1).
Lightning Lure cantrip. +5, pull 10 ft, 1d8 lightning (scaled).
Keto-Spawn (Deep-Sea Monster)
Large Monstrosity, Neutral Evil · CR 10 · 5,900 XP · Mini: Deep-sea angler/shark hybrid
AC 17 | HP 220 (21d10+84) | Speed 25 ft., swim 50 ft.
Senses: blindsight 30 ft. (angler lure) · Resist: cold
Climb Hull. Treat ship walls as non-difficult; can end turn on main deck.
Lure Hypnosis. Start of turn: one creature within 30 ft. that can see the lure DC 16 Wis or frightened+move toward it.
Siege. Double damage to objects (oar banks, rail).
Multiattack. Bite and two claws.
Bite. +10 to hit. Hit: 22 (3d10+6) piercing; grapple escape DC 16.
Claw. +10. Hit: 15 (2d8+6) slashing.
Swallow (Recharge 5–6). Grappled Medium target DC 16 Str or swallowed — 4d6 acid/turn; escape 25 HP to cut out.
Detect (1). Perception check.
Claw (1). One claw.
Thrash (2). Each creature within 10 ft. Dex DC 16 or 17 (5d6) bludgeoning and prone.
Lure Pulse (3). One creature within 30 ft. Wis DC 16 or frightened until end of next turn and pulled 15 ft. toward Keto-Spawn.
Clerk of the Blue Tithe (Quest Giver)
Medium Humanoid, Lawful Neutral · Religion +6 · Persuasion +5
Serves: Poseidon, Gods & Immortals
Temple accountant of Poseidon — tracking this fraud for three weeks
Motivation. Atlantean reavers are collecting a false sea-tax using Poseidon's name with a bound deep-beast as enforcement. He needs the party to authenticate the Bronze Tithe-Token to the Triton Wave-Caller — proving the fraud to someone with religious authority inside the operation.
Secret. Tried official channels first — told it was "under review." Suspects temple hierarchy is taking a cut. Insight DC 15 on his frustration when explaining why he came to the party instead.
RP Hook. Knows the Wave-Caller by name — served at the same tithe station three years ago. Persuasion DC 14 for an authentication letter that gives Advantage on the DC 14 check vs. Wave-Caller in Enc. 2.
Hook. Mist onto the trireme already underway; the enemy galley is hours behind — then suddenly alongside.
Bronze Tithe-Token
Wondrous Item (maguffin)
Poseidon’s authentic tax seal
Handout (20 words). "Show the true bronze when false kings claim the wave — the deep-beast bows to the stamp, not the spear."
Enc. 2. Advantage on Intimidation/Persuasion vs Atlanteans once.
Enc. 3. Action, brandish at Deep-Beast within 30 ft.: DC 15 Wis save or frightened 1 min and cannot Climb Hull for 1 round (once).
Reward Cards
Post-session keepables. Reward is the first tag. Mechanics below are for ongoing use after this oneshot.
Bronze Tithe-Token
Reward · Wondrous · 1/Long Rest
Mechanics. Once per long rest, as an action, brandish the token at one aquatic beast, monstrosity, or humanoid within 30 feet that claims sea-tax or boards ships. It must succeed on a DC 15 Wisdom saving throw or be frightened of you for 1 minute (repeat save at end of turns) and can't climb or board your vessel until the end of its next turn. While carried, you have advantage on one Charisma (Intimidation or Persuasion) check per short rest against creatures that respect Poseidon's law.
Appearance. A heavy bronze seal stamped with a trident and wave-tithe marks, cold as deep water.
Lore. Poseidon's authentic tax stamp, kept after false Atlantean kings were denied their stolen wave.
Quote. "The deep-beast bows to the stamp, not the spear." — Bronze Tithe-Token
Earn when: Authenticate Poseidon's true seal and turn back the deep-beast collecting for false kings.