Additional Netherdeep Monsters

Introduction

Here are 7 new monsters for Cael Morrow and the Netherdeep, to provide DMs with additional options of monsters to use, and ensure each fight is a memorable experience. The creatures range from simple plants to creatures warped by the Netherdeep. Encounter suggestions are also provided for each of these monsters.

Caelian Sea Snail

This large sea snail is native to the underwater ruins of Cael Morrow and is thought to be related to the land-based flail snail due to its innate magical nature. The sea snail, notably, has two antlers protruding from its skull, and propels itself with webbed claws, making it unusually dexterous for a such a creature.

Encounter. A couple of Caelian sea snails might be found instead of a swarm of sorrowfish in area M7b.

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Caelian Sea Snail

Large beast, unaligned

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• Armor Class 14 (natural armor)
• Hit Points 73 (7d10 + 35)
• Speed 15 ft., swim 15 ft.

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STR	DEX	CON	INT	WIS	CHA
16 (+3)	8 (-1)	20 (+5)	3 (-4)	12 (+1)	6 (-2)

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• Damage Immunities poison
• Condition Immunities poisoned
• Senses darkvision 60 ft., tremorsense 60 ft., passive Perception 11
• Languages —
• Challenge 4 (1,100 XP)

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Antimagic Shell. The sea snail has advantage on saving throws against spells, and any creature making a spell attack against the sea snail has disadvantage on the attack roll. If the sea snail succeeds on a saving throw against a spell or a spell attack misses it, an additional effect occurs, as determined by rolling a d6:

1-2. Confusion is cast centered on the sea snail. The sea snail is unaffected by this spell.

3-4. Haste is cast on the sea snail.

5-6. The sea snail's shell shines out an array of multicolored lights that extend out in a 30-foot radius until the beginning of the sea snail's turn.

Water Breathing. The sea snail can breathe only underwater.

Actions

Multiattack. The sea snail makes one antler and two claw attacks against one target.

Antler. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 8 (1d10 + 3) bludgeoning damage.

Claw. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) slashing damage.

Reactions

Shell Defense. The sea snail withdraws into its shell temporarily, gaining a +4 bonus to AC against a melee attack.

Corrupted Seadragon

A relative of the seahorse, seadragons are faster, tougher and have a breath weapon. The ruidium growths upon the seadragon cause mental anguish for nearby creatures.

Encounter. A couple of corrupted seadragons might be encountered instead of a slithering bloodfin in area N10.

Eye of the Deep

The Eye of the Deep, also known as a Seaholder, is a variant of beholder from previous editions of D&D. It is a floating skull, with a large central eye, two eyestalks, plus two pincers it uses for propulsion and grabbing prey.

Encounter. An eye of the deep might be found in area N13, replacing one of the scuttling serpentmaw.

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Eye of the Deep

Medium aberration, lawful evil

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• Armor Class 15 (natural armor)
• Hit Points 91 (14d8 + 28)
• Speed 0 ft., swim 20 ft.

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STR	DEX	CON	INT	WIS	CHA
16 (+3)	8 (-1)	14 (+2)	16 (+3)	14 (+2)	9 (-1)

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• Saving Throws Int +6, Cha +2
• Skills Perception +6
• Damage Resistances cold
• Condition Immunities prone
• Senses darkvision 120 ft., passive Perception 16
• Languages Deep Speech, telepathy 120 ft.
• Challenge 6 (2,300 XP)

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Amphibious. The eye of the deep can breathe air and water.

Actions

Multiattack. The eye of the deep makes four attacks: two with its pincers and one of each eye ray.

Pincer. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 3) piercing damage. The target is grappled (escape DC 14) if it is a Medium or smaller creature and the eye of the deep doesn't have a different target grappled in the pincer.

Eye Rays. The eye of the deep shoots an eye ray, choosing a target it sees within 120 feet of it:

1. Paralyzing Ray. The target must succeed on a DC 14 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

2. Cold Ray. The target must succeed on a DC 14 Dexterity saving throw, taking 27 (5d10) cold damage on a failed save, or half as much damage on a successful one.

Nautiloid

Gargantuan aberration, unaligned

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• Armor Class 17 (natural armor)
• Hit Points 232 (15d20 + 75)
• Speed 0 ft., swim 60 ft.

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STR	DEX	CON	INT	WIS	CHA
22 (+6)	8 (-1)	20 (+5)	14 (+2)	13 (+1)	6 (-3)

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• Damage Immunities cold, poison, psychic
• Senses darkvision 120 ft., passive Perception 11
• Languages understands Deep Speech but can't speak, telepathy 120 ft.
• Challenge 13 (10,000 XP)

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Amphibious. The nautiloid can breathe air and water.

Siege Monster. The nautiloid deals double damage to objects and structures.

Actions

Multiattack. The nautiloid makes three tentacle attacks.

Tentacle. Melee Weapon Attack: +10 to hit, reach 20 ft., one target. Hit: 16 (3d6 + 6) bludgeoning damage. On a successful hit, roll randomly to determine an additional effect imposed by the tentacle strike, linked to a plane of existence, rerolling duplicates:

1. Feywild. The targeted creature must succeed on a DC 14 Wisdom saving throw or be charmed by the nautiloid for 1 minute, or until the nautiloid harms the creature. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

2. Shadowfell. Magical darkness covers a 15-foot-radius area centered on the target.

3. Plane of Water. A current of water pushes the targeted creature back 30 feet.

4. Plane of Earth. The targeted creature must make a DC 14 Constitution saving throw. On a failed save, the creature begins to turn to stone and is restrained. It must repeat the saving throw at the end of its next turn. On a success, the effect ends. On a failure, the creature is petrified until freed by the greater restoration spell or similar magic.

5. Mount Celestia. The targeted creature takes an additional 7 (2d6) radiant damage.

6. Pandemonium. The targeted creature must succeed on a DC 14 Wisdom saving throw or suffer the effects of a confusion spell. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

7. Abyss. The targeted creature must succeed on a DC 14 Wisdom saving throw or be frightened for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

8. Avernus. The targeted creature takes an additional 7 (2d6) fire damage (halved in water).

Nautiloid

Nautiloids are giant sea creatures with psionic abilities. They are able to attune each of its tentacles to a different plane of existence, making it an unpredictable creature to face. The sheer size of these creatures means they are only found in the open ocean, so they cannot traverse the planar rift to Cael Morrow, nor can it enter Alyxian's Grottoes of Regret.

Nautiloids have almost been hunted to extinction by mind flayers, who have sought to turn these creatures into battleships. The shell is used for the hull, while the tentacles are telepathically connected to the mind flayer in order to traverse the ship between planes.

Encounter. A nautiloid might be found in area N1, asleep when first encountered, with tentacles wrapped around one of the statues for stability.

Red Kelp

This red aquatic plant feeds off of arcane energy. It is often found growing in the remains of sunken ruins or ships, or perhaps in the lair of a sea hag. While an individual plant is Small, a patch of red kelp can grow to enormous sizes.

Encounter. Red kelp might be found in areas M11 and N1.

Urchin Spikeshooter

These large ball of spikes float gently through the ocean, with the appearance of a spiky mobile fortress. It can shoot spines from its body at its prey, then drift over to devour the creature from a mouth hidden on its underside. After shooting spines from its body it is in a more vulnerable state. The spines regrow slowly over the period of a few days.

Encounter. The urchin spikeshooter might be found in area M13, replacing the death embrace.

Vampire Squid

Huge beast, unaligned

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• Armor Class 13 (natural armor)
• Hit Points 123 (13d12 + 39)
• Speed 10 ft., swim 40 ft.

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STR	DEX	CON	INT	WIS	CHA
18 (+4)	13 (+1)	17 (+3)	3 (-4)	10 (+0)	4 (-3)

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• Skills Perception +6, Stealth +4
• Senses darkvision 60 ft., passive Perception 16
• Languages —
• Challenge 8 (3,900 XP)

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Light Hypersensitivity. The squid takes 10 radiant damage when it starts its turn in bright light. While in bright light, it has disadvantage on attack rolls and ability checks.

Regeneration. The squid regains 10 hit points at the start of its turns. If the squid takes radiant damage, damage from holy water, or is in bright light, this trait doesn't function at the start of its next turn. The squid dies only if it starts its turn with 0 hit points and doesn't regenerate.

Water Breathing. The squid can breathe only underwater.

Actions

Multiattack. The squid makes two tentacle attacks. If a creature is grappled, it can make a bite attack on that creature in place of a tentacle attack.

Tentacle. Melee Weapon Attack: +8 to hit, reach 15 ft., one target. Hit: 13 (2d8 + 4) bludgeoning damage. If the target is a Large or smaller creature, it is grappled (escape DC 16). Until this grapple ends the target is restrained, and the squid can't use its tentacle on another target.

Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) piercing damage, plus 7 (2d6) necrotic damage. The target's hit point maximum is reduced by an amount equal to the necrotic damage taken, and the squid regains hit points equal to that amount. The reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.

Bonus Actions

Ink Cloud (1/Day). A 30-foot-radius cloud of ink extends all around the squid. The area is heavily obscured for 1 minute, although a significant current can disperse the ink.

Vampire Squid

No one knows how these giant squid-like creatures initially acquired their vampiristic traits, however it has established itself as one of the more feared creatures in the ocean's depths.

The Vampire Squid has two long tentacles that extend from its maw, which it uses to reel in and bite its prey.

Encounter. The vampire squid might be found in area N7, in place of the slithering bloodfin. The leader of the foes Alyxian faces in the vision, who morphs into the squid, might have vampiric teeth, foreshadowing the squid's abilities.

Art Credits

• p1 Caelian sea snail art from De reliquis animalibus exanguibus libri quatuor, post mortem eius editi: nempe de mollibus, crustaceis, testaceis et zoophytis by Ulisse Aldrovandi (public domain, image source).
  
• p2 Corrupted seadragon art from Sketchbook of Fishes by William Buelow Gould (public domain, image source).
  
• p3 Nautiloid art from Tiere der Urwelt by Heinrich Harder (public domain, image source).
  
• p4 Urchin Spikeshooter image taken by Didier Descouens (CC BY-SA 4.0, background removed, image source).
  
• p5 Vampire Squid art from Die Cephalopoden T. II: Myopsida, Octopoda by Carl Chun (public domain, image source).