ce gargantuan aquatic darvakka shadow undead 

Perception +36; greater darkvision, lifesense [object Object] feet

Skills Arcana +36, Athletics +39, Negative Energy Plane Lore +36, Religion +36, Shadow Plane Lore +36, Stealth +34

Str +11 Dex +6 Con +7 Int +8 Wis +8 Cha +7

AC  45; Fort +35, Ref +32, Will +36

HP 510, negative healing; Immunities cold, death effects, disease, paralyzed, poison, unconscious; Weaknesses good 15, silver 15

Midnight Depths (aura, cold, darkness, divine, necromancy, negative) 60 feet. A nasurgeth's entropy grows even stronger underwater. All water within the aura is completely dark (as 4th-level darkness). Magical light with a counteract level of 4th level or lower, along with magical light cantrips, are suppressed. A living creature entering or starting its turn in the aura takes 4d6 negative damage, and the creature also takes an additional 2d10 cold damage if it's in water (DC 39 basic Fortitude save). If it fails, it's also enfeebled 1 for 1 minute and pulled 10 feet toward the nasurgeth.

Sunlight Powerlessness As vanyver.

Spray Black Bile [R] Trigger The nasurgeth takes slashing or piercing damage from a critical hit, or a swallowed creature cuts itself free; Effect Darkness and negative energy spill out from the nasurgeth's wound, dealing 8d8 negative damage to creatures within 20 feet (DC 40 basic Fortitude).

Speed fly 60 feet, swim 80 feet

Melee [>] jaws +39 (magical, reach 15 feet), Damage 3d10+19 piercing plus 2d10 cold and Improved Grab

Melee [>] tail +39 (agile, magical, reach 20 feet), Damage 3d6+19 bludgeoning plus 2d10 cold

Divine Innate Spells DC 43; 8th eclipse burst (×3), harm (×3); 7th plane shift (to Material Plane, Negative Energy Plane, or Shadow Plane only), true seeing; Cantrips (10th) detect magic

Broken Barb [>] Requirements A creature is grabbed or restrained in the nasurgeth's jaws; Effect The nasurgeth breaks a tooth off in the target, who takes 3d10 persistent bleed damage and is no longer grabbed or restrained. If the target is adjacent to a surface, the tooth also pins it in place, making it immobilized (Escape DC 45).

Ravenous Void [>>>] The nasurgeth barrels forward with their mouth open, Swimming twice in a straight line and moving through the spaces of Huge or smaller creatures. The nasurgeth deals the damage of their jaws Strike to each creature whose space they enter (DC 45 basic Reflex save). Any creature that critically fails is automatically Swallowed Whole.

Swallow Whole [>] Huge, 2d10+9 bludgeoning, Rupture 40. A living creature that ends its turn swallowed whole by a nasurgeth becomes drained 1 or increases its drained condition by 1, and the nasurgeth gains 20 temporary Hit Points. A creature whose drained condition increases to 5 in this way dies.

Book of the Dead, page 85.