Wastrilith (CR 17)
AC: 25 (-2 size, +4 Dex, +13 natural), touch 12, flat-footed 21
Hit Dice: 15d8+60 (127 hp)
Fort +13, Ref +15, Will +12
Speed: 30 ft., swim 80 ft.
Space: 15 ft./15 ft.
Base Attack +15; Grapple +32
Attack: Bite +22 melee
Full Attack: Bite +22 melee and 2 claws +17 melee
Damage: Bite 2d6+9, claw 2d4+4
Special Attacks/Actions: Breath weapon, spell-like abilities
Abilities: Str 29, Dex 18, Con 19, Int 14, Wis 12, Cha 19
Special Qualities: Break summoning, cold immunity, fire vulnerability, immunity to water, outsider traits, SR 20, water mastery
Feats: Combat Reflexes; Dodge; Improved Initiative; Iron Will; Lightning Reflexes; Mobility
Skills: Bluff +5, Concentration +18, Diplomacy +20, Disguise +4 (+6 acting), Escape Artist +18, Hide +10, Intimidate +28, Knowledge (arcana) +1S, Knowledge (the planes) +15, Listen +15, Move Silently +18, Spellcraft +18, Spot s-IS, Survival +1 (+3 on other planes), Swim +31, and Use Rope +4 (+6 binding)
Advancement: 16-21 HD (Huge); 22-45 HD (Gargantuan)
Climate/Terrain: Any aquatic (Abyss)
Treasure/Possessions: Double standard
Breath Weapon (Su): Cone of boiling water, 3d10 points of damage, 60 feet, every 1d4 rounds; Reflex DC 21 half.
Break Summoning (Ex): If summoned via a summon monster spell, a wastrilith can make an opposed Wisdom check to break free of the summoning. If it succeeds, it then goes on a rampage, attacking the summoner.
Spell-like Abilities: At will - blasphemy, control water, deeper darkness, desecrate, detect good, detect law, fear, greater dispelling, read magic, suggestion, telekinesis, teleport without error (self plus 50 pounds of objects only), tongues (self only), unhallow, unholy blight, wall of ice; 3/day - symbol (any), unholy aura. Caster level 15th; save DC 14 + spell level.
Three times per day, a wastrilith can cast summon monster IX as a 17th-level wizard. It can only summon aquatic and water-based creatures, such as fiendish sharks or squids and water elementals.
Immunity to Water (Ex): Wastriliths are immune to attacks that are based on water.
Telepathy (Su): Wastriliths can communicate telepathically with any creature within 100 feet that has a language.
Water Mastery (Ex): A wastrilith gains a +1 bonus on its attack and damage rolls if its opponent is touching water.
Skills: Wastriliths have a +8 racial bonus on Intimidate checks. They have a +8 racial bonus on any Swim check to perform some special action or avoid a hazard and can always choose to take 10 on Swim checks, even if distracted or endangered.
Creatures with the aquatic subtype always have swim speeds and thus can move in water without making Swim checks. An aquatic creature can breathe underwater. It cannot also breathe air unless it has the amphibious special quality.
A subtype usually applied only to outsiders native to the chaotic-aligned Outer Planes. Most creatures that have this subtype also have chaotic alignments; however, if their alignments change they still retain the subtype. Any effect that depends on alignment affects a creature with this subtype as if the creature has a chaotic alignment, no matter what its alignment actually is. The creature also suffers effects according to its actual alignment. A creature with the chaotic subtype overcomes damage reduction as if its natural weapons and any weapons it wields were chaotic-aligned (see Damage Reduction).
A subtype usually applied only to outsiders native to the evil-aligned Outer Planes. Evil outsiders are also called fiends. Most creatures that have this subtype also have evil alignments; however, if their alignments change, they still retain the subtype. Any effect that depends on alignment affects a creature with this subtype as if the creature has an evil alignment, no matter what its alignment actually is. The creature also suffers effects according to its actual alignment. A creature with the evil subtype overcomes damage reduction as if its natural weapons and any weapons it wields were evil-aligned (see Damage Reduction).
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.