Sepron the Contradiction

Sepron is a great serpent that lurks in the cloudsea of Aetheris , having made its layer not far from the ruins of Heliomea. The serpent originates from the elemental plane of air, however, after the abandonment of the heavens when Aetheris became closer aligned with the elemental plane of air, Sepron somehow made its way to the once divine plane.
Sepron is the undisputable apex predator of the cloudsea, strong enough to even fell a Tempest Whale. Sepron prefers to hunt its prey by ambushing them from the clouds, constricting them, and biting at them viciously until the creature passes. If it hunts multiple creatures, Sepron will still attempt an ambush, but rather than using its body to restrain it, Sepron instead strikes multiple of the creatures with its body with great force in an attempt to knock them out before devouring them whole.
The serpent makes its layer at the Submerged Isle, to the north of the Icara settlement. It hunts the cloudsea surrounding the sunken palace for large game or packs of creatures. As a result, the Icara tend to avoid venturing far from their city. The Icara of Heliomea refer to the beast as Sepron the Conqueror of the clouds. However, the beast is known by a different name in tales passed around in Meydia. There, it is referred to as Sepron the Contradiction. This name was bestowed upon it due to legends of a large aquatic snake being spread through the province, which should be impossible given the size of the lakes in Meydia. These tails likely originate from the few people that have spotted Sepron dip out of the cloud bed that covers the province, which over generations became distorted speaking of a water serpent instead of one from the clouds.
Due to Sepron originating from the elemental plane of air, it is strongly aligned with the magical winds. Through an inherit ritual known as the Call of Typhoon, Sepron can tap into the elemental energies of air despite no longer being in its birth plane.

Traits

• Cloud Delver: Sepron can swim through clouds as if they were water.
• Weakspot: The AC of Sepron's head is reduced by 2 when defending against an attack that does Slashing, Piercing, Bludgeoning, or force damage.
• Constructor: Sepron has advantage on checks made to grapple or restrain a large creature or larger and imposes disadvantage on Dexterity checks made to avoid its Restrain action.
• Unending Breath: Sepron can hold its breath indefinitely while not incapacitated.
• Dominating: Sepron is immune to negative status conditions from physical sources unless the acting creature is of size huge or greater, and from magical sources unless the spellslot used is of 5th level or greater.
• Ambusher: During a surprise round, Sepron may use its bonus action to use the Dash action.  

Actions

• Multiattack: Sepron makes three attacks, one bite and two bashes. Instead of making a bite attack, Sepron may take the breath-out action of Cloud Breath.
• Bite: Melee Weapon Attack: +11 to hit, reach 5 ft., 1 target. Hit: 24 (3d10 + 7) piercing damage, plus an additional 14 (4d6) force damage when under the effect of Call of Typhoon.
• Bash: Melee Weapon Attack: +8 to hit, reach 5 ft., 1 target. Hit: 14 (2d8 + 5) bludgeoning damage, plus an additional 7 (2d7) force damage when under the effect of Call of Typhoon. Sepron strikes out with its body, slamming part of itself into its target violently. On a hit, the targeted creature must succeed on a DC 16 Strength saving throw or be knocked back 5 ft. and fall prone. On a critical fail, the creature falls unconscious until the end of its next turn.
• Restrain: Sepron attempts to restrain a creature that is of medium size or larger. If the creature is of medium size, it must succeed on a DC 17 Dexterity saving throw or become restrained by Sepron. If the creature is of large size or above, Sepron makes a Strength (athletics) check contested by the target's Strength (athletics) or Dexterity (acrobatics) check. To escape being restrained, a restrained creature must spend its action to do so by succeeding on a DC 19 Strength check.
• Squeeze: As a bonus action, Sepron squeezes all creatures it has restrained, dealing 16 (2d8 +7) bludgeoning damage to each of them.
• Cloud Breath: As a bonus action, Sepron scoops up a chunk of clouds, retraining them in its mouth by holding its breath. On any of its subsequent turns, Sepron may spend its action to breathe out the clouds, creating a 10 ft. radius cloud centered on a spot within 30 ft. of its mouth. The cloud disperses after 1 minute. Creatures in the cloud have their vision reduced to 5 ft. Immediately after creating the cloud, Sepron may use its Bite attack on a creature inside the cloud. Sepron has advantage on this attack if the target relies on sight to track Sepron. While holding its breath, Sepron cannot use its bite attack.
• Storming Winds (cooldown 4-5 turns): While under the effect of Call of Typhoon, Sepron coils around a circular area with a maximum 15 ft. radius, creating a brief tornado-like updraft in this area. All creatures within this area take 14 (4d6) force damage and must make a DC 17 Strength saving throw. On a failure, a creature is carried off by the winds, being blown 30 ft. up in the air and onto a random location within the affected area, before being slammed down by a second wind. The creature takes an additional 10 (3d6) bludgeoning damage and fall prone.
• Call of Typhoon (once per day): Sepron lets out a loud roar as it calls upon the elemental magic of air. For the next hour, Sepron's Bite and Bash attacks deal additional force damage and it can use its Storming Winds action. Additionally, Sepron spawns 8 elemental wind sprites. These sprites are small volatile air elementals that will drift towards the nearest creature other than Sepron or another creature aligned to the element of air at a speed of 10 ft. per turn. Once making contact with another creature, the sprite will explode, dealing 9 (2d8) Forced damage in a 5 ft. area around itself, vanishing in the process. The sprites, being made out of air, are barely visible to the naked eye. A creature must succeed on a DC 20 Wisdom (perception throw) in order to detect a sprite, noting one as a faint disruption in the airflow. Creatures with a passive perception of 24 or higher automatically detect the sprites when within 15 ft. This range increases by 5 ft. for every additional point in their passive perception. A sprite will detonate prematurely after taking 10 hit points worth of damage. They have the same resistances and immunities as air elementals.

Legendary Actions

Sepron can take up to 3 legendary actions each round.

• Bash

Layer Actions

• Tidlewave: When in its layer, Sepron may dive into the cloudsea and stir up a large title wave. The majority of the submerged isle will be covered with clouds, restricting sight to 10 ft. The clouds disperse after 5 rounds. The tidal wavewill also flud creatures from the cloudsea onto the isle, some of which will try to flee while others attack the players out of agitation. Sepron will remain submerged in the cloudsea until all cloudsea creatures have been killed or escaped its layer. While submerged, Sepron may spend its action to snatch and consume a dead or unconscious creature, healing itself for 18 (4d8) hitpoints.

STR	DEX	CON	INT	WIS	CHA
24 (+7)	18 (+4)	18 (+4)	8 (-1)	14 (+2)	7 (-2)

Type: Gargantuan Beast
Armor Class: 18
Hit Points: 425
Speed: 50 ft. flying, 75 ft. swimming
Proficiency: +6
Saving Throws: STR +13, WIS +8
Skills: Stealth +10, Survival +8, Intimidation +4
Damage Resistance: Lightning, Force, Radiant; non-magical Piercing, Slashing, Bludgeoning
Condition Immunities: Blinded
Senses: blindsight 60 ft., darkvision 120 ft., smell 600 ft.
Languages: -
Challenge: 21 (33000xp)