Monolith, Water (CR 17)

Gargantuan Elemental (Water and Extraplanar)
Alignment: Usually neutral
Initiative: +6 (Dex); Senses: darkvision 60 ft., Listen +43, and Spot +43
Languages: Aquan

AC: 27 (-4 size, +6 Dex, +15 natural), touch 12, flat-footed 21
Hit Dice: 36d8+255 (417 hp); DR: 15/-
Fort +27, Ref +20, Will +16
Speed: 30 ft., swim 120 ft.
Space: 20 ft./20 ft.
Base Attack +27; Grapple +53
Attack: Slam +38 melee
Full Attack: 2 slams +38 melee
Damage: Slam 6d8+14/19-20
Special Attacks/Actions: Drench, vortex, water mastery
Abilities: Str 38, Dex 22, Con 25, Int 12, Wis 15, Cha 17
Special Qualities: elemental traits
Feats: Alertness; Awesome Blow; Cleave; Dodge; Great Cleave; Improved Bull Rush; Improved Critical (slam); Improved Natural Attack; Improved Sunder; Iron Will; Lightning Reflexes; Power Attack; Weapon Focus (slam)
Skills: Diplomacy +5, Intimidate +16, Jump +27, Listen +43, Sense Motive +15, Spot +43, and Swim +22.
Advancement: 37-54 HD (Gargantuan)
Climate/Terrain: Elemental Plane of Water
Organization: Solitary
Treasure/Possessions: None

Source: Complete Arcane

Drench (Ex): A water monolith's touch puts out torches, campfires, exposed lanterns, and other open flames of non-magical origin of they are Huge or smaller. The creature can dispel magical fire it touches, as if using greater dispel magic (caster level 20th).

Vortex (Su): A water monolith can transform itself into a whirlpool at will as a standard action, provided it is underwater. It can remain in that form as long as it likes. In vortex form, a monolith can move through the water or along the bottom at its swim speed. The vortex is 10 feet wide at the base, up to 50 feet wide it the top, and up to 80 feet tall. The monolith controls the exact height, but it must be at least 20 feet. A water monolith's movement while in vortex form does not provoke attacks of opportunity, even if the monolith enters the space another creature occupies. Another creature might be caught in the vortex if it touches or enters the vortex, or if the monolith moves into or through the creature's space.

Huge or smaller creatures take damage when caught in a vortex and may be swept up by it. An affected creature must succeed on a DC 42 Reflex save when it comes into contact with a vortex or take 4d6 points of damage. It must also succeed on a second DC 42 Reflex save or be picked up bodily and held suspended in the powerful currents, automatically taking the indicated damage each round. An affected creature is allowed a Reflex save each round to escape the vortex. The creature still takes damage, but can leave if the save is successful. The save DC is Strength-based.

A creature trapped in a vortex cannot move except to go where the water monolith carries it or to escape the vortex. It can otherwise act normally, but must make a Concentration check (DC 20 + spell level) to cast a spell. Creatures caught in the vortex take a -4 penalty to Dexterity and a -2 penalty on attack rolls. A monolith can have only as many creatures trapped inside the vortex at one time as will fit inside the vortex's volume.

A water monolith can eject any carried creatures whenever it wishes, depositing them wherever the vortex happens to be. A summoned monolith always ejects trapped creatures before returning to its home plane.

If the vortex's base touches the surface beneath a body of water, it creates a swirling cloud of debris. This cloud is centered on the elemental and has a diameter equal to half the vortex's height. The cloud obscures all vision, including darkvision, beyond 5 feet. Creatures 5 feet away have concealment, while those farther away have total concealment. Those caught in the cloud must make a Concentration check (DC 15 + spell level) to cast a spell.

A water monolith in vortex form cannot make slam attacks and does not threaten the area around it.

Water Mastery (Ex): A water monolith gains a +2 bonus on attack rolls and damage rolls if both it and its opponent are touching water. If the opponent or the elemental are touching the ground, the monolith takes a -4 penalty on attack rolls and damage rolls.

A water monolith can easily affect the movement of ships in any squares it threatens as a full-round action, overturning any craft up to 180 feet long, or halting and holding motionless a ship as long as 360 feet. Larger ships can be reduced to half speed for as long as they remain threatened by the monolith.

Skills: A water monolith has a +8 racial bonus on any Swim check to perform some special action or avoid a hazard. It can always choose to take 10 on a Swim check, even if distracted or endangered. It can use the run action while swimming, provided it swims in a straight line.

Water monoliths are almost as strong as earth monoliths, but they are much quicker and more agile. They prefer to fight in water, where they can disappear beneath the waves and outmaneuver their foes, but in any instance a water monolith cannot venture more than 300 feet from the body of water from which it was conjured.

Water Subtype

This subtype usually is used for elementals and outsiders with a connection to the Elemental Plane of Water. Creatures with the water subtype always have swim speeds and can move in water without making Swim checks. A water creature can breathe underwater and usually can breathe air as well.

Extraplanar Subtype

A subtype applied to any creature when it is on a plane other than its native plane. A creature that travels the planes can gain or lose this subtype as it goes from plane to plane. This book assumes that encounters with creatures take place on the Material Plane, and every creature whose native plane is not the Material Plane has the extraplanar subtype (but would not have when on its home plane). An extraplanar creatures usually has a home plane mentioned in its description. These home planes are taken from the Great Wheel cosmology of the D&D game (see Chapter 5 of the Dungeon Master's Guide). If your campaign uses a different cosmology, you will need to assign different home planes to extraplanar creatures.

Creatures not labeled as extraplanar are natives of the Material Plane, and they gain the extraplanar subtype if they leave the Material Plane. No creature has the extraplanar subtype when it is on a transitive plane; the transitive planes in the D&D cosmology are the Astral Plane, the Ethereal Plane, and the Plane of Shadow.