Apepthys

Amphibious. Apepthys can breathe air and water.

Aura of Dread. Any creature hostile to Apepthys that starts its turn within 30 feet must succeed on a DC 20 Wisdom saving throw or be frightened for 1 minute. A frightened target can repeat the save at the end of each of its turns.

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

Multiattack. Apepthys makes three attacks: one with its bite and two with its tail.

Bite. Melee Weapon Attack: +16 to hit, reach 15 ft., one target.
Hit: 36 (4d12 + 9) piercing damage plus 18 (4d8) lightning damage.

Tail. Melee Weapon Attack: +16 to hit, reach 20 ft., one target.
Hit: 28 (4d8 + 9) bludgeoning damage. The target must succeed on a DC 24 Strength saving throw or be knocked prone.

Tidal Wave (Recharge 5-6). Apepthys unleashes a massive wave in a 60-foot cone. Each creature in that area must make a DC 22 Strength saving throw, taking 54 (12d8) bludgeoning damage and being knocked prone on a failed save, or half as much damage and not knocked prone on a successful one.

Stormcall (Recharge 6). Apepthys summons a violent storm around itself for 1 minute. During this time:

• Heavy rain and howling wind reduce visibility to 30 feet.

• Ranged weapon attacks beyond 30 feet have disadvantage.

• At the start of each of Apepthys' turns, it may deal 18 (4d8) lightning damage to all creatures within 20 feet.

1. Tidal Surge (Recharge 5–6).
Apepthys thrashes its body, generating a sudden wave of pressurized water. Each creature within 30 ft. must succeed on a DC 23 Strength saving throw or be pushed up to 20 ft. away and knocked prone. The area becomes difficult terrain until the start of Apepthys’s next turn.

2. Abyssal Glare.
The serpent focuses one burning eye on a single creature it can see within 120 ft. That creature must succeed on a DC 21 Wisdom saving throw or be frightened until the end of its next turn. If already frightened, the creature instead takes 14 (4d6) psychic damage as the serpent’s will crushes its mind.

3. Serpent’s Coil.
If a Huge or smaller creature is grappled by Apepthys, the serpent tightens its coils. The grappled creature takes 27 (6d8) bludgeoning damage automatically, and Apepthys may move up to 10 ft., dragging the creature with it without provoking opportunity attacks.

4. Ocean’s Whisper (Mythic Phase Only).
After dropping below half its hit points, Apepthys can use this Bonus Action once per round. It emits a deep, resonant hum that reverberates through the water and stone of Alri itself. One Blue Crystal Anchor within 120 ft. flickers and destabilizes. At the end of Apepthys’s next turn, that crystal releases a Surge of Arcane Energy, dealing 45 (10d8) force damage to all creatures within 30 ft. of it (DC 23 Dex save for half).

5. Recoil of the Deep.
Immediately after taking damage from a melee attack, Apepthys may lash its tail as a reflexive motion against one creature within 15 ft. The target must make a DC 22 Dexterity save or take 22 (4d10) bludgeoning damage and be knocked prone.

6. Abyssal Regeneration (Recharge 6).
Apepthys channels the depths through its scales, regaining 40 hit points and shedding any one condition currently affecting it (except petrified). While in contact with seawater, this heals 60 hit points instead.

1. Wrath of the Depths.
When Apepthys takes 50 or more damage from a single source, it releases a burst of oceanic fury. Each creature within 20 ft. must make a DC 23 Strength saving throw or take 21 (6d6) bludgeoning damage and be pushed 15 ft. away.
If this reaction occurs while submerged, it also creates a cloud of churning silt (heavily obscured area, 30 ft. radius) until the end of its next turn.

2. Serpent’s Reflex.
When a creature moves out of Apepthys’s melee range, the serpent may make one tail attack or bite attack against that creature. On a hit, it deals an additional 14 (4d6) lightning damage, as residual magic crackles from its scales.

3. Abyssal Retaliation (Recharge 5–6).
When hit by a spell or magical effect, Apepthys can channel the curse that binds it. The caster must make a DC 22 Constitution saving throw or take 27 (6d8) force damage and be staggered until the end of their next turn (speed reduced to 0, can’t take reactions).
If the caster is concentrating on a spell, they make the save at disadvantage.

4. Shatter the Chains (Mythic Phase Only).
When reduced to 0 HP for the first time, Apepthys roars with such force that its body ignites with blue crystal light, restoring it to 300 HP and beginning its Mythic Phase. All creatures within 120 ft. must make a DC 24 Wisdom saving throw or be blinded and deafened until the end of their next turn as the serpent’s rage cracks reality itself.

5. Guardian of the Abyss.
When a creature within 30 ft. of a Blue Crystal Anchor is attacked, Apepthys may interpose its magic through the crystal. The attacker takes 14 (4d6) cold damage, and their attack roll is made with disadvantage as shimmering wards of abyssal energy deflect their strike.

6. Snap of the Leviathan.
When a creature misses Apepthys with a melee attack, it may make a bite attack against that creature as a reaction. On a hit, the target is grappled (escape DC 21) and restrained until freed.

Apepthys can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature’s turn. Apepthys regains spent legendary actions at the start of its turn.

• Detect. Apepthys makes a Wisdom (Perception) check.

• Tail Attack. Apepthys makes a tail attack.

• Lightning Surge (Costs 2 Actions). Apepthys releases a bolt of lightning at one target it can see within 120 feet. The target must make a DC 22 Dexterity saving throw, taking 36 (8d8) lightning damage on a failed save, or half damage on a success.

Apepthys' Mythic Trait: "Wrath of the Deep Currents"

When Apepthys is reduced to 0 hit points, it does not die or fall unconscious. Instead, it thrashes in a massive roar, summoning the full power of the ocean’s fury. Apepthys regains 300 hit points and enters its Mythic Form for the rest of the battle. While in this form, Apepthys gains new abilities, enhanced resistances, and access to Mythic Actions.

Mythic Actions

Apepthys gains 3 Mythic Actions per round, which can be spent like Legendary Actions. These actions are in addition to its normal Legendary Actions.

1. Titanic Slam (Costs 1 Action)
Apepthys slams its massive body into the ground or an enemy.

• Melee Weapon Attack: +16 to hit, reach 20 ft., one target.

• Hit: 45 (8d8 + 9) bludgeoning damage, and the target must succeed on a DC 24 Strength saving throw or be stunned until the end of Apepthys's next turn.

2. Crushing Whirlpool (Costs 2 Actions)
A swirling whirlpool of crushing water erupts around Apepthys in a 40-foot radius for 1 minute (concentration). Creatures starting their turns in the whirlpool must succeed on a DC 22 Strength saving throw or take 27 (6d8) bludgeoning damage and be restrained until the start of their next turn.
A creature can repeat the save at the end of its turns.

3. Abyssal Roar (Costs 3 Actions)
Apepthys unleashes an earth-shattering roar causing shockwaves around it (60-foot radius).
Each creature in that area must succeed on a DC 22 Constitution saving throw or be deafened and take 36 (8d8) thunder damage on a failed save, or half on a success.