Aquatic / PirateD&D 5eFrom the DepthsGM Resources

50 Aquatic Enemies for for 6th-10th 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. I will also be presenting encounter seeds for these villains at each tier. This week I bring you enemies and encounters for parties of 6th through 10th level characters.

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

Make sure to check out Shawn Ellsworth’s overview of 10 Awesome Monsters for Aquatic Encounters, as well as his articles for eight other terrains right here on Tribality.

Looking for encounter ideas for these creatures? Help yourself to half-a-dozen and let me know how your players enjoy them.


For the purposes of this series, villains are defined as individuals that act as either instigators of complex local, city-wide, or country-wide plots, or creatures that can act as the main antagonist for one or more adventures. I’ve typically limited Villains to creatures with a minimum of 10 Intelligence. This led me to some surprising discoveries. For example, I didn’t realize that several low-level undead creatures have impressive Intelligence scores, including banshees, ghosts, ghasts, revenants, wraiths, and even will-o’-wisps!

I’ve also included a few surface creatures that make excellent villains and can be easily adapted to an aquatic campaign (such as the mind flayers and yuan-ti), as well as one or more new villains for you to use against your party.

Bonus Villain: a new, CR 8 merrow: the hand of Demogorgon


Lieutenants act as the higher-level minions of villains. They are smart enough to instigate plots of their own, typically at the behest of their villainous masters. Alternately, lieutenants may act as Villains for the lowest level parties at each tier. For example, a young black dragon (CR 7) can act as a main villain for a party of 6th level PCs, as long as it has enough minions and an interesting enough lair to make the encounter enjoyable.

Bonus Lieutenant: you can find the CR 5 wereshark and CR 4 merrow hunter-seeker in the previous article of this series.


Minions are the lowest-tier servants of the villains and lieutenants, or beasts that can be used as wandering monsters, guards, or random encounters. Lieutenants (and even Villains) of lower-level parties can easily be the Minions of higher-level Villains. This category also includes creatures with Intelligence scores below 10, including beasts, constructs, plants, and undead that can be used to flesh out encounters.

Keep in mind that large numbers of lower CR creatures can also make for interesting encounters. For example, sharks make great encounters in small numbers, but some species of sharks, including the hammerhead (use stats for hunter shark) swim in shoals of hundreds and even thousands! Though a combat using 100 hunter sharks might appear tedious, it can be a terrifying experience and a challenge for any party. At 45 hit points and 13 damage per bite, even these CR 2 creatures can deal significant damage to 11th level or higher PCs, especially after a party member gets damaged and triggers the shark’s blood frenzy.

Since the Lieutenants (and even Villains) of lower-tiers can be used as Minions in higher-level encounters, there is plenty of material to use. I have, however, included one or more new creatures you can use against your players when inspiration has hit.

Bonus Minion: the Ulat-Kini (aka: Skum) are presented both as a monster and as a playable PC race.


In the accompanying article for each tier, I will provide general plot outlines and story seeds for you to use to create encounters for your aquatic games. I will include options for campaigns focused entirely on aquatic races as well as for surface campaigns looking to shake things up.

For 1st-5th level encounter seeds, check out our previous Encounters post.

6th-10th Level


Challenge Rating 7
  • Black Dragon (Young)
  • Mind Flayer (add Amphibious or Aquatic traits)
  • Yuan-Ti Abomination (add the Amphibious or Aquatic traits)
Challenge Rating 8
  • Assassin (any aquatic race or creature with Intelligence 12 or higher; increase CR by 1 if already greater than 8) 
  • Green Dragon (Young)
  • Merrow, Hand of Demogorgon (see below)
  • Spirit Naga
Challenge Rating 10
  • Aboleth
Challenge Rating 11
  • Behir (add the Amphibious trait)
  • Marid
Challenge Rating 12
  • Archmage (can be of any aquatic race or creature capable of having an Intelligence of 18 or higher; increase CR by 1 if already greater than 12)
Challenge Rating 13
  • Storm Giant


Challenge Rating 4
  • Ghost
Challenge Rating 5
Challenge Rating 6
  • Green Hag, Mage (add Intelligence score and spellcasting of the Mage NPC)
  • Sea Hag, Mage (add Intelligence score and spellcasting of the Mage NPC)
Challenge Rating 7
  • Black Dragon (Young)
  • Mind Flayer (add Amphibious or Aquatic traits)
  • Yuan-Ti Abomination (add the Amphibious or Aquatic traits)
Challenge Rating 8
  • Assassin (any aquatic race or creature with Intelligence 12 or higher; increase CR by 1 if already greater than 8)
  • Green Dragon (Young)
Challenge Rating 11
  • Behir (add the Amphibious trait)


In addition to those listed below, you can use any of the minions/pets from the 1st-5th level Enemies list. For creatures with CR 1 or less, use the creatures in larger numbers, such as shoals of hunter sharks numbering in the dozens, or “swarms” of constrictor snakes.

Challenge Rating 1/2
  • Ulat-Kini (aka: Skum) see below
Challenge Rating 2
  • Druid (can be of any aquatic race or creature capable of having an Intelligence and Wisdom of 12 or higher; replace quarterstaff with spear)
  • Constrictor Snake, Giant (add Amphibious trait)
  • Ghast
  • Merrow 
  • Ooze, Ochre Jelly (add trait that oozes do not require air)
  • Plesiosaurus 
  • Poltergeist (see Ghost)
  • Priest (can be of any aquatic race or creature capable of having an Intelligence and Wisdom of 12 or higher; replace mace with shortsword or trident)
  • Sea Hag
  • Shark, Hunter 
  • Snake, Poisonous Swarm
  • Will-o’-Wisp 
Challenge Rating 3
  • Green Hag
  • Knight (koalinth, kuo-toa, locathah, lizardfolk, merfolk, sahuagin; replace greatsword with trident)
  • Veteran (koalinth, kuo-toa, locathah, lizardfolk, merfolk, sahuagin; replace longsword with extra shortsword, or both swords with trident)
  • Sea Hag, Cleric or Druid (add Wisdom score and spellcasting of the Cleric or Druid NPC)
  • Water Weird
  • Wight
  • Yuan-Ti Malison ( add the Amphibious or Aquatic traits; add Swim speed 30’; merfolk features in place of human features)
Challenge Rating 4
  • Black Pudding (add trait that oozes do not require air)
  • Chuul
  • Ghost
  • Green Hag, Cleric or Druid (add Wisdom score and spellcasting of the Cleric or Druid NPC)
  • Merrow, Hunter-Seeker
Challenge Rating 5
  • Crocodile, Giant
  • Flesh Golem (add 30 ft. Swim speed)
  • Gladiator (koalinth, kuo-toa, locathah, lizardfolk, merfolk, sahuagin)
  • Shark, Giant
  • Scrags (trolls with the Amphibious or Water Breathing traits)
  • Shambling Mound (seaweed)
  • Umber Hulk (add the Amphibious or Water Breathing traits; Swim speed 3o ft.)
Challenge Rating 6
  • Invisible Stalker (water elemental variant)
Challenge Rating 8

Merrow Hand of Demogorgon

Large monstrosity, chaotic evil

Armor Class 15 (natural)
Hit Points 90 (10d10+30)
Speed 10 ft.; swim 40 ft.
Initiative +6

Str 18 (+4) Dex 14 (+2) Con 16 (+3) Int 14 (+2) Wis 16 (+3) Cha 16 (+3)

Damage Resistances cold, lightning, bludgeoning, piercing, slashing from nonmagical weapons.
Damage Immunities
Condition Immunities
charmed, frightened, poisoned
Saving Throws Con +6, Int +5, Wis +6
Skills Arcane +5, Intimidate +9, Perception +6, Religion +5, Stealth +5
Senses darkvision 120 ft., Passive Perception 16
Languages Abyssal, Aquan
Challenge 8 (3,900xp)


Amphibious. The hand of Demogorgon can breath both air and water.
Blood Frenzy. The hand of Demogorgon gains advantage on attacks against any creature at less than maximum hit points.

Spellcasting. The naga is a lOth-level spellcaster. Its spellcasting ability is Wisdom (spell save DC 14, +6 to hit with spell attacks). It has the following cleric spells prepared:

Cantrips (at will): chill touch, guidance, mending, resistance, sacred lightning (as sacred flame), thaumaturgy
1st level (4 slots): bane, command, false life, inflict wounds, ray of sickness 
2nd level (3 slots): aid, blindness/deafness, hold person, ray of enfeeblement
3rd level (3 slots): animate dead, bestow curse, revivify, vampiric touch
4th level (3 slots): blight, banishment, death ward, freedom of movement
5th level (2 slots): antilife shell, insect plague (millions of marine arthropods), cloudkill (poisonous ink cloud)

Touch of Death. Whenever the hand of Demogorgon hits a target with a melee attack, it may inflict an extra 25 necrotic damage to the target. It may not use this ability again until it takes a short rest.
Inescapable Destruction. The attacks of the hand of Demogorgon ignore necrotic resistance, but not immunity.


Multiattack. The hand of Demogorgon makes two attacks: either any two melee weapon attacks, or one cantrip plus a melee weapon attack. Alternately, the hand may make a claw attack and either a vampiric touch or inflict wounds spell attack against the same target. All other spells require the hand’s action to cast.

Bite. +7 to hit, reach 5 ft., one target,  14 (2d8+4) piercing damage, plus 5 (1d8) necrotic damage.
Claws. +7 to hit, reach 5 ft., one target,  12 (2d6+4) slashing damage, plus 5 (1d8) necrotic damage.
Chill Touch. +6 to hit, range 120 ft., two targets within 5 ft. of each other, 9 (2d8) necrotic damage and the target cannot regain hit points until the beginning of the hand’s next turn.
Sacred Lightning. Dex save (DC 14) or take 9 (2d8) lightning damage. Attack ignores cover.
Inflict Wounds. +6 to hit, reach 5ft., one target, 16 (3d10) necrotic damage. +6 (1d10) necrotic damage per spell slot above 1st.
Ray of Sickness. +6 to hit, range 60ft., one target, 9 (2d8) poison damage and target must succeed on a DC 14 Con save or become poisoned for 1 round. +5 (1d8) necrotic damage per spell slot above 1st.
Vampiric Touch. (Concentration, 1 minute) +6 to hit, reach 5ft., one target, 11 (3d6) necrotic damage and the hand heals hit points equal to half the damage. +4 (1d6) necrotic damage per spell slot above 1st.
Harpoon. +7 to hit, reach 5 ft. or range 20/60 ft., one target,  14 (2d8+4) piercing damage and the target must succeed on a DC 13 Dexterity saving throw or become impaled. An impaled creature is restrained. A critical hit forces the target to make the Dexterity save at disadvantage. If an impaled creature is Huge or smaller, it must succeed on a Strength contest against the hand of Demogorgon or be pulled up to 20 feet toward the hand. The hand of Demogorgon may not make a harpoon attack as long as a target is impaled. The impaled creature, or any creature adjacent to them, may use an action to end the restrained condition. Doing so inflicts an additional 14 (2d8+4) piercing damage. The damage can be prevented by a successful DC 15 Medicine check made after 1 minute of treatment.

Ulat-Kini (aka Skum)

Medium humanoid (ulat-kini), lawful evil

Armor Class 13 (natural)
Hit Points 29 (3d8+12)
Speed 20 ft.; swim 40 ft.
Initiative +0

Str 15 (+2) Dex 13 (+1) Con 17 (+3) Int 10 (+0) Wis 10 (+0) Cha 6 (-2)

Saving Throws Wis +2
Damage Resistances
Condition Immunities charmed
Skills Athletics +4, Deception +2, Perception +2, Stealth +5
Senses darkvision 60 ft., Passive Perception 14
Languages Aboleth, Aquan
Challenge 1/2

Amphibious. The ulat-kini can breath both air and water.
Ancient Slaves. The mind of the ulat-kini is resistant to mind controlling abilities of all creatures except aboleth. They have immunity to the charmed and frightened conditions and proficiency with Wisdom saving throws, but loose these advantages when dealing with the spells and psionic powers of aboleth.


Bite. +4 to hit, reach 5 ft., one target, 6 (1d6+2) piercing damage.
Trident. +4 to hit, reach 5 ft., one target,  8 (1d8+2) piercing damage.


From Paizo SRD:

“Ulat-kini (skum) are the most prolific and successful of the countless races created by the aboleths to serve as slaves. At the height of the aboleth empire, skum were legion and their armies waged many wars upon the land, yet now that the aboleths are in decline, skum have been set loose to manage on their own.

“For the most part, the skum have been less than successful at this endeavor, and today they exist in a shadow of their previous multitude, most of them dwelling deep underground in slowly crumbling ruins left standing only because their enemies have lost interest in pursuing the now-won war against these fish-like humanoids. Skum have even lost their own name—only the most erudite and wise of their kind remember that they were once known as the ulat-kini. Today, most identify themselves with the racial epithet applied to them by surface-dwellers—“skum.”

“Skum do not age, and barring death by violence or disease, they can live forever. Unfortunately, this near immortality is crippled by the fact that skum are incapable of reproducing among themselves, for all skum are male. The aboleths did not want their slave race to prosper without their permission. Yet terribly, this does not mean that skum cannot breed. Originally created from human stock, skum can impregnate humans, and the children issued from such unholy unions are invariably deformed. Those who are not born skum undergo gradual transformations throughout their lives, and when they would normally die of old age, such hybrids instead go through “the change,” shedding their wrinkled flesh and transforming into one of the ulat-kini. While most skum tribes lack the drive to perpetuate their race and would prefer to languish in their hideous sunken ruins, tribes settling offshore of remotely populated coastlines seem to be on the rise. Some such communities raid villages for breeding stock, but a few more insidious tribes form alliances with these desperate folk, providing protection and bounty from the sea in return for wives.”


Ulat-Kini PC Traits

Ability Score Increase. Your Constitution increases by 2, and Strength increases by 1. Your Charisma decreases by 2.
Age. Ulat-kini are immortal. You are immune to aging effects.
Alignment. As former slaves to the aboleth, the vast majority of ulat-kini are programed to be lawful evil. Player character ulat-kini separate from their tribes for many reasons, some of which may be the breakdown of their ancient aboleth programing. Ulat-kini PCs may be of any alignment.
Size. Ulat-kini are similar in size to humans, though they are muscular and hardy. Your size is medium.
Speed. Your base walking speed is 20 ft. You have a swim speed of 40 ft.
Former Slaves. Ulat-kini were created as a slave race to the aboleth, and therefor were granted some protection against the magic of their master’s enemies. You gain advantage on saves against charm and fear spells, and gain proficiency with one of the following saving throws: Intelligence, Wisdom, or Charisma. You make all saving throws against aboleth spells and psionic powers at disadvantage, including against charm and fear spells.
Bite. You may use your action to make a bite attack. Your bite deals 1d6 + Strength modifier piercing damage.
Naturally Deceptive. You gain proficiency in Deception and Stealth.
Amphibious. You can breath both air and water.
Languages. You speak, read and write Aboleth and Aquan, as well as one other language (typically Undercommon or Common)