Nasurgeth

Creature 20

Gargantuan
aquatic
darvakka
shadow
undead
unholy

Perception: +36; greater darkvision, lifesense 60 feet
Languages: Chthonian, Common, Diabolic, Necril, telepathy 100 feet
Skills: Arcana +36, Athletics +39, Religion +36, Shadow Plane Lore +36, Stealth +34, The Void Lore +36; Str +11, Dex +6, Con +7, Int +8, Wis +8, Cha +7

Greater Darkvision

Telepathy 100 feet (aura, magical, mental)

Lifesense 60 feet

AC: 45; Fort +35, Ref +32, Will +36
HP: 510, void healing; Immunities cold, death effects, disease, paralyzed, poison, unconscious, bleed; Weaknesses holy 15, silver 15

Midnight Depths (aura, cold, darkness, divine, void) 60 feet. A nasurgeth's entropy grows even stronger underwater. All water within the aura is completely dark (as 4th-rank Darkness). Magical light with a counteract rank 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 void damage, and the creature also takes an additional 2d10 cold damage if it's in water (DC 39 basic Fortitude). If it fails, it's also Enfeebled 1 for 1 minute and pulled 10 feet toward the nasurgeth.

Spray Black Bile ⟲ Trigger The nasurgeth takes slashing or piercing damage from a critical hit, or a swallowed creature cuts itself free

Effect Darkness and void energy spill out from the nasurgeth's wound, dealing 8d8 void damage to creatures within 20 feet (DC 40 basic Fortitude).

Sunlight Powerlessness A nasurgeth caught in sunlight is Stunned 2 and Clumsy 2.

Void Healing

Speed: 0 feet, fly 60 feet, swim 80 feet

Melee ◆ jaws +39 (magical, reach 15 feet, unarmed), Damage 3d10+19 piercing plus 2d10 cold plus Improved Grab

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

Divine Innate Spells DC 43, attack +35; 8th eclipse burst, harm; 7th interplanar teleport (to the universe, void, or netherworld only), truesight; Cantrips (1st) 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 bleed 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). Any creature that critically fails is automatically Swallowed Whole.

Swallow Whole ◆ (attack) 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.

Improved Grab ◇

Source: Pathfinder Monster Core 2

Running this fight? Add the nasurgeth to the initiative tracker: type its name and the AC, hit points and Perception for initiative fill in, and the book button shows this stat block mid-fight.