Amethyst River Wyvern

Amphibious. The wyvern can breathe air and water.

Camouflage. A creature the wyvern touches and everything it wears or carries becomes invisible upon will of the wyvern. If the target drops an item or removes it, the item is no longer invisible, and if the target tries to attack or cast a spell, the ability ends early. Only sight is affected, all other senses by untargeted creatures still function as normal. Wyvern and target have all senses intact during the ability.

Spellcasting. The Wyvern is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 17, +9 to hit with spell attacks).

Primal Roar. Casting Time: 1 action Range: Self (30-foot radius) Duration: Up to 1 minute

The wyvern roars, bellowing out a terrifying sound to all that hear it. Each creature in a 30-foot cone must succeed on a Wisdom saving throw or drop whatever it is holding and become frightened for the duration.
While frightened by this spell, a creature must take the Dash action and move away from they wyvern by the safest available route on each of its turns, unless there is nowhere to move. If the creature ends its turn in a location where it doesn’t have line of sight to the wyvern, the creature can make a Wisdom saving throw. On a successful save, the spell ends for that creature.

Depthsurge. Casting Time: 1 standard action
Range: 400 ft.
Area: 20 ft. radius
Duration: Instantaneous

The wyvern expels a powerful jet of water from its mouth outward in a massive surge, as if driven by a powerful explosion.
Each creature or object in the area is subject to damage equal to 2d6 + caster level.
Any creature struck by this attack must then succeed on a Constitution save or be driven 10 feet away from the centre of the blast.

Airy Water. Casting Time: 1 standard action
Range: Within 5 ft.
Area: 20-ft.-radius emanation centred on the wyvern
Duration: 10 min.

This spell turns normal water (or watery solutions) into a frothy substance that is as breathable as air.
Both air-breathing and water-breathing creatures within the area can breathe normally.
Moving through airy water is easier than moving through normal water.
Creatures can instead use their land speed to move along the bottom at their normal speed.
Creatures walking on the bottom of the body of water in question use their normal speed while this spell is active or if they don't have a swim speed.
Airy water negates underwater combat penalties for all melee attacks, although ranged attacks still take the normal underwater penalty.

Drown. Casting Time: 1 standard action
Range: Close (25 ft. + 5 ft./2 levels)
Target: One living creature
Duration: Instantaneous
Saving Throw: Fortitude negates
Spell Resistance: Yes

The wyvern creates water in the lungs of the subject, causing it to begin drowning.
The subject's hit points immediately drop to 0, and it falls unconscious.
In the next round, it loses another hit point (bringing its hp to -1) and is dying.
In the following round, it dies.
Coughing and other attempts by the subject to physically expel the water from its lungs are useless.
However, another creature can stabilize the subject with a DC 15 Heal check before death.
Undead, constructs, creatures that do not need to breathe, and creatures that can breathe water are unaffected by this spell.

Control Water. Casting Time: 1 standard action
Range: Long (400 ft. + 40 ft./level)
Area: Water in a volume of 10 ft./level by 10 ft./level by 2 ft.
Duration: 10 min.

Until the spell ends, the wyvern controls any freestanding water inside an area it chooses that is a cube up to 100 feet on a side. It can choose from any of the following effects when it casts this spell. As an action on its turn, it can repeat the same effect or choose a different one.
Flood: The wyvern causes the water level of all standing water in the area to rise by as much as 20 feet. If the area includes a shore, the flooding water spills over onto dry land.
If the wyvern chooses an area in a large body of water, it instead creates a 20-foot tall wave that travels from one side of the area to the other and then crashes down. Any vehicles in the wave’s path are carried with it to the other side. Any vehicles struck by the wave have a 25 percent chance of capsizing.
The water level remains elevated until the spell ends or the wyvern chooses a different effect. If this effect produced a wave, the wave repeats on the start of your next turn while the flood effect lasts.
Part Water: The wyvern causes water in the area to move apart and create a trench. The trench extends across the spell’s area, and the separated water forms a wall to either side. The trench remains until the spell ends or the wyvern chooses a different effect. The water then slowly fills in the trench over the course of the next round until the normal water level is restored.
Redirect Flow: The wyvern causes flowing water in the area to move in a direction you choose, even if the water has to flow over obstacles, up walls, or in other unlikely directions. The water in the area moves as the wyvern directs it, but once it moves beyond the spell’s area, it resumes its flow based on the terrain conditions. The water continues to move in the direction it choses until the spell ends or it chooses a different effect.
Whirlpool: This effect requires a body of water at least 50 feet square and 25 feet deep. The wyvern causes a whirlpool to form in the centre of the area. The whirlpool forms a vortex that is 5 feet wide at the base, up to 50 feet wide at the top, and 25 feet tall. Any creature or object in the water and within 25 feet of the vortex is pulled 10 feet toward it.
When a creature enters the vortex for the first time on a turn or starts its turn there, it must make a Strength saving throw. On a failed save, the creature takes 2d8 bludgeoning damage and is caught in the vortex until the spell ends. On a successful save, the creature takes half damage, isn't caught in the vortex and can swim away automatically. A creature caught in the vortex can use its action to try to swim away making another Strength saving throw. The first time each turn that an object enters the vortex, the object takes 2d8 bludgeoning damage; this damage occurs each round it remains in the vortex.

Multiattack. The wyvern makes two attacks: one with its bite and one with its claws. 

Bite. Melee Weapon Attack: +7 to hit, reach 10 ft., one creature. Hit: 11 (2d6 + 4) piercing damage.

Claws. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) slashing damage.

Steam Breath. The wyvern exhales a 30-foot cone of scalding steam. Each creature in that area must succeed on a DC 12 dexterity saving throw, taking 10 (3d6) fire damage on a failed save, or half as much damage on a successful one. Being underwater doesn't grant resistance against this damage.

Recovery Breath. The wyvern exhales a 15-foot cone of healing energy. Each creature of the dragon's choice in that area recovers 7 (1d8 + 3) hit points and is freed from any curse, disease, or poison.