Above this brobdingnagian, whalelike creature's cavernous maw of freakish teeth, multiple eyes peer out in different directions.
Astral Leviathan CR 18
N Colossal outsider (extraplanar)
Init +6; Senses astral locating, blindsight 180 ft., darkvision 60 ft., low-light vision; Perception +31
AC 34, touch 4, flat-footed 32 (+2 Dex, +30 natural, –8 size)
hp 310 (20d10+200); regeneration 5 (acid and fire)
Fort +24, Ref +8, Will +16
DR 10/adamantine; Immune cold; Resist electricity 30, fire 30
Speed fly 90 ft. (average)
Melee bite +24 (4d6+12/19–20 plus grab), 2 slams +24 (2d8+12), tail slap +19 (4d6+6)
Space 30 ft.; Reach 30 ft.
Special Attacks fast swallow, gulping tide, swallow whole (4d6+18 damage, AC 25, 31 hp)
Spell-Like Abilities (CL 20th; concentration +22)
Str 35, Dex 14, Con 31, Int 6, Wis 15, Cha 14
Base Atk +20; CMB +40 (+42 bull rush, +44 grapple); CMD 52 (54 vs. bull rush, can't be tripped)
Feats Blind-Fight, Cleave, Combat Reflexes, Great Fortitude, Improved Bull Rush, Improved Critical (bite), Improved Initiative, Iron Will, Power Attack, Skill Focus (Perception)
Languages telepathy 30 ft.
Environment any (Astral Plane)
Organization solitary or pod (2–5 plus 1–2 young)
Astral Locating (Su) An astral leviathan automatically knows the distance and direction to any place on the Astral Plane it has ever visited. Once per day it can use this ability to determine the location of a creature on the Astral Plane (as if using locate creature with unlimited range).
Gulping Tide (Ex) An astral leviathan can create a 60-foot cone of roiling astral material, pulling all Large or smaller creatures and objects into its mouth so it can swallow them. Any creature in the area that succeeds at a DC 30 Fortitude save moves up to 60 feet toward the cone's origin; creatures that fail are swallowed. The leviathan can use this ability only once per minute. The save DC is Constitution-based.
An astral leviathan is an immense predator that patrols the silvery void of the Astral Plane in search of food and new experiences. Dangerous if provoked, it is intelligent enough to be reasoned with, though most visitors to that plane mistakenly believe it is just a beast. It requires only a minimal amount of physical food, as it primarily sustains itself on planar energies (particularly those radiating from natural portals to other planes) and invisible streamers of astral dust. Astral leviathans are curious about types of creatures they've never met before and places they haven't visited. Civilized inhabitants of the Astral Plane might befriend, bribe, or tame leviathans, using them as cargo vessels or navigators on journeys to remote locations. More savage races enslave them with enchantments and hooked barbs and use them for the same purpose.
An astral leviathan is approximately 70 feet long and weighs 60 tons.