The Diver

The Diver
Large Aberration, ???
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AC 20
HP 243 (18d10)
Speed 20 ft, Swim 20 ft. 
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STR: 26 (+8) 
DEX: 10 (+0) 
CON: 28 (+9) 
INT: 7 (-2) 
WIS: 16 (+3) 
CHA: 6 (-2)
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Saving Throws - Strength +16, Constitution +17, Wisdom +11
Skills - Athletics +24, Stealth +16, Survival +11
Resistances - Cold, Fire, Force, Lightning
Damage Immunities - Poison, Psychic
Condition Immunities - Charmed, Exhaustion, Frightened, Petrified, Poisoned 
Senses - Darkvision 120 ft., Blindsense 20 ft.,  Passive Perception 13
Languages - Understands Common, Primordial (Aquan), and Abyssal
Challenge - 25
Proficiency Bonus - +8
Habitat - Coastal, Underwater
Treasure - The Diver's Suit
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TRAITS

Legendary Resistance (3/Day) - If the Diver fails a saving throw, it can choose to succeed instead.

Alien Mind - Magic and other features can't determine the Diver’s creature type. If a creature tries to read the Diver’s thoughts, that creature must succeed on a DC 20 Intelligence saving throw or have the stunned condition for 1 minute and begins Suffocating, as if it was underwater (a creature who can breathe underwater is immune to the Suffocating effect). The stunned creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Immutable Form - The Diver is immune to any spell or effect that would alter its form.

Magic Resistance - The Diver has advantage on saving throws against spells and other magical effects.

Unusual Nature - The Diver does not need to breathe, eat, drink, or sleep. Additionally, the Diver can move along any surface with its hands free. 

Devourer of Souls - Any creature within 15 ft. of the Diver has Disadvantage on Death Saving Throws. If a creature dies within 15 ft. of the Diver, it regains a number of hit points equal to the hit point maximum of the creature who died. Additionally, that creature cannot be revived by magical means until the Diver is killed. 
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ACTIONS

Multiattack - The Diver makes 3 attacks with its Crushing Claw. Any of these attacks may be replaced by a Phantom Harpoon attack. 

Crushing Claw - Melee Attack Roll. +14 to hit, reach 5-ft. Hit: 26 (4d8+8) Bludgeoning damage and the target is Grappled (Escape DC22) if it is Huge or smaller. If this attack is used against a creature already Grappled by the Diver, it automatically hits, and deals 26 (4d8+8) Bludgeoning damage. Grappling a creature in this way does not reduce the Diver’s speed when it moves. 

Phantom Harpoon - Melee or Ranged Attack Roll. +14 to hit, reach 10-ft. or range 60-ft. Hit: 16 (2d8+8) Force damage and 14 (4d6) Lightning damage. After throwing the harpoon, it dissipates and reappears in the Diver’s hand. 

Defensive Shock (Recharge 5-6) - The Diver emits a burst of electricity around it in a 15-ft Emanation. All creatures within the Emanation must make a DC 22 Constitution saving throw. Failure: 44 (8d10) Lightning damage and the creature is Stunned until the end of its next turn. Success: Half damage and the creature is not Stunned.
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Bonus Actions

Spectral Sea Mines (Recharge 6) - The Diver chooses up to 6 points within 60-ft., conjuring strange, semi-transparent, mechanical orbs that float in place. These orbs are small objects, with an AC of 19, and 15 hit points. They are immune to all forms of non-magical damage. 

When an orb is destroyed or a creature moves within 5-ft. of one, it detonates, per the Detonate ability. 

Detonate - The Diver detonates one of its sea mines. All creatures within 10-ft. of the mine must make a DC 22 Dexterity saving throw. Failure: 16 (3d10) Force damage and the creature is knocked Prone. Success: Half damage and the creature is not knocked Prone.  
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Reactions

Reel ‘em In - Upon hitting a target with its Phantom Harpoon, the Diver can use its Reaction to create a tether between it and the target. The target must succeed on a DC 22 Strength staving throw. Failure: The target is pulled in a straight line toward the Diver, until it is within 10-ft of it. Success: No effect. 
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Legendary Actions
Legendary Action Uses: 3. Immediately after another creature's turn, The Diver can expend a use to take one of the following actions. The dragon regains all expended uses at the start of each of its turns.

Charge - The Diver moves up to twice its Speed and can make one melee attack with its Crushing Claw or Phantom Harpoon. If it moves at least 20-ft. in a straight line before the attack, the attack deals an additional 9 (2d8) Force damage. 

Detonate - The Diver uses its Detonate ability.
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NOTES

An urban myth. A ghost story. A tall tale. 

Among coastal towns and cities, sailors and fishermen, The Diver is a creature that haunts many a mind. Something of a bogeyman, it goes by many names. The Deep Dweller. Devil of the Depths. The Eye. The Captain. 

A vengeful spirit? A strange construct? A demonic entity? In truth, nobody quite knows what this creature is, but the truth lies somewhere in between. The Diver itself is nothing…but the Diver’s Suit, is another story. A strange parasitic creature from another plane that feeds off the souls of the living to power itself. 

From stories and reports of this creature, it is a relentless foe that often tries to single out individuals to prey upon. If faced with a group, it uses its strange powers to try to capture and escape with a single person to feed on, before returning and attempting the cycle over again. 

It is unknown how many of these creatures exist. Many believe it to just be the one, but with so many coastal communities having tales of the creature, others are skeptical.
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LOOT

The Diver’s Suit

Armor (Heavy, Special), Legendary, Requires Attunement

“Upon defeating The Diver, the light within the suit blanks out as it crumples to the ground. A creature who attunes to the Diver’s Suit gains a number of benefits, but these benefits come with a terrible curse.

This curse deepens over time, strengthening the powers of the suit but sinking it’s wearer further into the crushing depths until they become the very creature they destroyed to get it.”
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While wearing the suit, a creature’s AC becomes 20. This armor has a minimum Strength requirement of 15 and a creature cannot gain a bonus to AC from their Dexterity modifier. It does not impose Disadvantage on Stealth checks, despite its weight. While in the suit, your speed is reduced by 10ft. 

Dormant

While in its Dormant stage, the suit can be donned and doffed as per normal heavy armor. 

Hulking Form - While wearing the suit, you count as one size larger for carrying capacity, pushing, dragging, lifting, and grappling. 

Crushing Claw - Attached to the armor is a powerful claw that can be used as a weapon and works seamlessly as if it were your own hand. Attacks with this claw use your Strength modifier and deal 2d8 Bludgeoning damage. On a hit with the Claw, the target becomes Grappled and further claw attacks against the creature automatically hit. 

Closed System - While wearing the helmet of the suit, the suit becomes airtight, though a strange approximation of your voice still emanates from the helmet when you speak. It provides you with clean oxygen and protects you from harmful gasses and vapors. While wearing the helmet you have Disadvantage on ability checks using Charisma.

The Curse Awakens… - The first time you are reduced to 0 HP while wearing this armor, the curse within the suit becomes active. At this stage of the curse, you have Disadvantage on Death Saving Throws, as the suit seeks to consume your soul. The curse and attunement to this item can only be broken by a Remove Curse spell. Any other negative effects from the suit wear off within a week of the curse being broken. 

 If you ever re-attune to the armor, the curse picks up where it left off. 

Gestating

While in its Gestating stage, your body has become reliant on the suit. You are still able to remove it, but while outside of the suit, you have Disadvantage on all Strength, Dexterity, and Constitution rolls. 

Phantom Harpoon - While you have a hand free, you are able to summon a spectral harpoon (No action required) and use it to make a melee or ranged attack using your Strength modifier. Attacks with the Harpoon deal 1d8 Force damage and 2d6 Lightning damage. After making the attack, the harpoon reappears in your hand. 

Safe and Snug -  While in the suit with the helmet on, you gain Resistance to Cold and Fire damage, but the suit seems to slowly leak seawater whenever you are wearing it. 

Rushing Water - You can take the Dash action as a Bonus Action and may move up to triple your speed when doing so, propelled along by a spray of seawater. 

The Curse Deepens… - When a creature with 15 or more hit dice is reduced to 0 hit points within 15 feet of you, it must make a DC 22 Constitution saving throw. On a failure, the creature immediately dies and you are healed for an amount equal to that creature’s maximum hit points. That creature cannot be revived until you break the curse and un-attune to the suit…Unfortunately, removing the curse and the suit now requires the Regenerate spell to be cast before Remove Curse, lest the wearer’s body waste away outside of the suit. 

Emergent

While in its Emergent stage, your body has become so reliant on your suit, that you cannot live for long outside of it. Each minute you spend without the suit and helmet on, you take 10d6 Poison damage, as you have become so reliant on the suit, the outside atmosphere is now toxic to you. This damage cannot be reduced or negated by any means. 

Defensive Shock - As an Action, you emit a burst of electricity around yourself in a 15-ft Emanation. All creatures within the Emanation must make a DC 18 Constitution saving throw.

Failure: 4d8 Lightning damage and the creature is Stunned. Success: Half damage, and the creature is not stunned.

You may use this ability once and regain the ability to use it on a Short or Long Rest. 

Spectral Sea Mines - As a Bonus Action, choose a number of points equal to your Proficiency modifier within 60-ft. You conjure strange, semi-transparent, mechanical orbs that float in place. These orbs are small objects, with an AC of 19, and 15 hit points. They are immune to all forms of non-magical damage. 

When an orb is destroyed or a creature moves within 5 ft. of one, it detonates, per the Detonate ability. 

You may use this ability once and regain the ability to use it on a Long Rest. 

Detonate - As a Bonus Action, you detonate one of your sea mines. All creatures within 10 ft. of the mine must make a DC 18 Dexterity saving throw. Failure: 16 Force damage and the creature is knocked Prone. Success: Half damage and the creature is not knocked Prone.  

The Curse Fulfilled… - Whenever you reduce a creature to 0 hit points, you must make a Wisdom saving throw equal to 10 + the number of times you have made this saving throw since your last Long Rest. On a failure, what's left of your body and soul is taken by the suit, and you are transformed into The Diver. Nothing can restore you short of a Wish spell.