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14 Aquatic Encounter Seeds for 1st-5th level Characters

In this series I will be presenting creatures you can use for villains, lieutenants, minions, and wild encounters for 5th edition aquatic games, as well as encounter seeds for these villains at each tier.

This week I bring you aquatic encounter ideas for parties of 1st through 5th level characters. You can find lists of the villains, lieutenants, and minions referred to in last week’s Enemies post.

Though these monster lists and story seeds are inspired by 5th edition, they can be used as adventure ideas for any fantasy RPG.


Undead Villains

Unlike surface cultures, aquatic races rarely bury their dead in the ground. Civilized races that gather in large underwater cities sometimes create necropolises from coral reefs and atolls, ritually weigh down bodies to drop into drenches or the Deep, or wrap bodies in organic cocoons and float them in seaweed forests until they decay. Though the first and last options create versions of graveyards that can be manipulated by negative energy the same as surface graveyards do, crevices on the edge of large settlements or trenches that have been used by nomadic cultures for hundreds if not thousands of years to bury dead provide a dangerous amount of material for necromancers and aberrations from the deep.

The undead villains listed all have Intelligence scores of 10 or higher and can be used as hooks in a variety of adventures.

  • Ghasts are highly intelligent ghouls, which is to say they have basic humanoid levels of intellect. This intelligence is less representative of book knowledge and more on cunning. Ghasts often lead packs of ghouls and their motivations are primal.
  • Banshees and ghosts can have a wide range of motivations depending on how they died or what is preventing them from moving on. Both creatures can act more as quest givers than direct opponents.
  • Revenants are obsessed with destroying the person(s) who gave them a cruel and undeserved death. As with banshees and ghosts, revenants need not be antagonistic to the PCs and may instead enlist their aid.
  • Wights and wraiths are formed from the souls of the living that made (or make) a deal with malevolent forces. Each has the ability to generate more undead minions, and even one of these creatures existing near a small, unprotected village can wreck havoc.

Undead Story Seeds

  • A pack of ghouls are making strategic attacks against aquaculture farms on the outskirts of a medium-size town. The farms are far enough away that three of them have been attacked with no survivors over several weeks. The PCs either have friends on one of the farms or are approached by family members or merchants who deal with the farms to investigate. The pack is led by a ghast who drives the ghouls to only attack the farms farthest from civilization granting them more time to feed and get away.
  • The banshee/poltergeist/ghost of the elven cleric of a sea god haunts the remains of a sunken ship. The creature’s wails and twisted divine power has called numerous sea creatures to the area including a large shoal of hunter sharks and a wyrmling green dragon that has allied itself with the spirit and made the wreck its home. The ship was a cargo vessel hauling silks, spices, alchemical supplies, and a divine artifact of questionable origin that the spirit is protecting. The silks, spices, and supplies may be common on the surface but are rare under the waves and can be valuable to the right buyer.
  • A sahuagin salenti was murdered by his kin after they discovered his “compromised” soul. The salenti is spotted by one or more PCs at night within the boundary of a settlement that would never allow sahuagin inside without raising an alarm. You can stretch the sightings over several days or weeks and have only one PC see it, or spread the sightings out between characters. The salenti eventually approaches the PCs (or they track it down using divination magic or psionics) for help in destroying its former kinsmen, specifically the brute who murdered him.

Hag Villains

Hags are a classic villain in aquatic campaigns and though the listed hags have relatively low Challenge Ratings (2 and 3), they can easily be adapted to higher level threats by adding the resistances and spellcasting abilities of the Mage and Archmage located in the back of the Monster Manual.

Hags are most commonly encountered alone, but through necessity they may gather in covens of three. The three members need not be the same type of hag, though they often are. Hags seek classic villainous goals such as vengeance for a wrong, power over others, manipulation of arcane energies, etc.

Story Seeds

  • A hag sends her minions (mephits, merfolk zombies, scouts, shadows, ghouls, giant octopuses) to kidnap a person of power to blackmail their parent/guardian and the PCs must get them back.
  • A hag has discovered the location of an ancient temple holding a magic item, gem infused with knowledge, aboleth artifact, etc. The PCs learn about the existence of the temple at the same time as the hag from a local sage, or learn of the potentially disastrous discovery through a vision from the gods, a former slave/servant of the hag, or some other means.
  • A hag has decided to “spawn” by kidnapping a local peasant child. Authorities are too busy to put resources toward finding the child so the parents come to the PCs.

Humanoid/Piscinoid Villains

Humanoid/piscinoid villains are the most varied creatures above and below the waves. You can run any style of game below the surface that you would above the surface with few changes.

Story Seeds

  • A small village of merfolk or locathah are hounded by marrow raiders and come to the “big city” for help, a la “The Seven Samurai” or “Magnificent Seven”.
  • A cult of Panzuriel is becoming active in the PC’s local city.
  • The PCs are asked by the local ruler to deliver supplies and trade goods to allies on the surface that live on a small island chain. The PCs are attacked by pirates on the surface and underwater on the way. The pirates are from a neighboring island chain and have allied with a koalinth tribe to barricade the PC’s allies from receiving supplies or aid.
  • The PCs inherit a map that leads to a lost cave complex where one of the PC’s ancestors, a paranoid but powerful arcane researcher, performed experiments. A variety of traps, animated guardians, and twisted aberrations guard the complex.

Monstrous Villains

The two main monstrous villains that work well at the lowest tier of adventures are the mind flayers and the yuan-ti. Though it may sound brutal to put the PCs against CR 7 creatures, the lieutenants and minions of these beasts can create a string of adventures that the PCs must navigate before eventually discovering their ultimate foe.

Story Seeds

  • A rogue mind flayer (one that is not part of a collective) is attempting to gain power within a major city. The party can run into a number of the creature’s minions: a small group of doppelgängers disguised as a now-dead merchant family that are gathering intel while living off the family’s riches; a cult of locathah or merfolk that believe the flayer to be the living embodiment of an ancient god; a malenti wereshark that acts as the flayer’s body guard and consigliere; or all of the above.
  • A yuan-ti abomination has uncovered an ancient temple, buried long ago after the fall of the yuan-ti empire. The abomination, along with its minions, are kidnapping locals to sacrifice in a ritual that will summon a demon or devil and grant the abomination control over it. A serpent god worshiping cult of locathah or merfolk may follow the yuan-ti, as well as one or more yuan-ti malisons and any number of purebloods. If you want to increase the creep-factor, include a bone naga as one of the abomination’s lieutenants. Bone naga are created by yuan-ti as a way to punish their naga enemies by breaking the naga’s immortality cycle. The bone naga’s impressive Intelligence make them ideal lieutenants for any yuan-ti villains.

Draconic Villain

Even at the lowest tier, dragons can be used as antagonists for your PCs. Young green and black dragons can act as masterminds behind numerous plots using a range of minions, and perhaps even wyrmling younger siblings as lieutenants. Merrow and the new merrow hunter-seekers make excellent draconic allies, as do kuo-toa, reptilian beasts such as snakes, and even shambling mounds and other plant-like creatures.

Story Seeds

  • A young dragon has laid claim to a string of atolls that house a community offering food, rest, and supplies along a minor trade route. The atolls are located hundreds of miles from the nearest settlement. The PCs must free the community’s terrorized residents and re-open trade by driving off or killing the dragon and its allies. If using a green dragon then shambling mounds, hunter sharks, giant sharks, water weirds, elementals, and swarms of poisonous snakes make excellent allies. If using a black dragon, then scrags, koalinth mercenaries, skeletons, zombies, ghosts, and other undead are ideal.
  • The drunken uncle of one of the PCs has always talked about his glorious years as a dragon slayer, though no one has ever believed him. Until the day the child of one of his victims shows up for revenge. The hunter could approach the party asking for protection in the form of “joining him for one last great dragon hunt”, or the party might stumble across the creature stalking the former hunter through the streets/wilderness and drive it off. Any color of dragon can be used for this particular scenario, which may affect the party’s desire to help. If using a metallic dragon, the party may negotiate the return of an important artifact or family heirloom to the young wyrm instead of fighting it.

Image: Merfolk from the Pathfinder RPG