X’sval, Av atar of the Unspeakable One
This crimson, noisome mass spreads in shreds and tendrils over a large area, a bubbling conglomeration of lumps, tentacles, sensory organs, and laughing half-faces, like a vomited tumor of madness.

X’sval (CR 7; XP 3,200)
CE Large outsider (chaotic, evil, extraplanar)
Init +3; Senses darkvision 60 ft.; Perception +9
Aura confusion (30 ft.; W-DC 16), unnatural aura (30 ft.)
AC 20, touch 13, flat-footed 16
(+3 Dex, +1 dodge, +7 natural, -1 size)
hp 69 (6d10+36)
Fort +11, Ref +8, Will +2
DR 10/law and good; Defensive Abilities amorphous; Immune polymorph; SR 18
Speed 20 ft., fly 10 ft. (perfect)
Melee 2 slams +12 (2d6+7 plus essence disruption, grab)
Space 10 ft.; Reach 5 ft.
Special Attacks consume (W-DC 15), possession (W-DC 15)
Spell-Like Abilities (CL 6th; concentration +8)
1/day—blasphemy (W-DC 19)
3/day—cloudkill (F-DC 17)
Str 25, Dex 16, Con 23, Int 10, Wis 10, Cha 14
Base Atk +6; CMB +14 (+18 grapple); CMD 28 (can’t be tripped)
Feats Dodge, Mobility, Stealthy
Skills Escape Artist+18, Knowledge (planes) +9, Perception +9, Spellcraft +9, Stealth +18, Survival +9; Racial Modifiers +4 Escape Artist, +4 Stealth
Languages Abyssal, Infernal
SQ compression
Environment planes (Realms Beyond)
Organization solitary, or group (2-5)
Treasure none
Special Abilities
Confusion Aura (Ex) Any creature that comes within 30 ft. of the x’sval must make a Will save (DC 15) or suffer the effects of the confusion spell for 6 rounds. If the creature is still within range when the confusion wears off they must attempt a save again. Once the character is successful they are immune to this effect for 24 hours. The save DC is Charisma-based.
Consume (Su) As a full-round action, a x’sval can consume any creature it has grappled, absorbing its essence into it. The victim is allowed a Will save (DC 15) to resist. A consumed victim ceases to exist, along with all its possessions, and cannot be brought back by any means short of wish or miracle. The x’sval gains 1 consumption point per Hit Dice of the victim. For every 8 consumption points it gains, the x’sval’s hit dice increases by one.
Essence Disruption (Su) The touch of the x’sval carries the taint of the Unspeakable One. Any creature struck must make a Will save (DC 15) or suffer an additional 1d4 points of bleed damage and 1 point of Dexterity damage. The save DC is Charisma-based.
Possession (Su) As a full-round action, a x’sval can possess any creature it has grappled. The victim is allowed a Will save (DC 15) to resist this effect. If the victim fails, the some of the x’sval flows into the victim through its mouth and nose and seizes telepathic control of the victim in all ways. This process deals damage to the x’sval equal to the victim’s remaining hit points, and if the x’sval has enough hit points it could possess many creatures. The victim is now treated as a chaotic evil creature. The x’sval can be forced from the victim by rendering the victim unconscious, killing the victim, or targeting it with a dismissal or similar banishing effect. The save DC is Charisma-based.

Manifested fragments of the Unspeakable One’s persona, x’sval are often summoned by greedy seekers after power. When in a temple or place of worship, they divide their attentions between possessing minions to wreak havoc, or increasing their own power by consuming terrified victims. On the Material Plane, they grow stronger and stronger the longer they stay, forcing mere mortals to take notice of the power of the Unspeakable One. Though they resemble oozes, they are not and they bear an evil cunning for devastion that is rarely equaled.

On Porphyra
The Yellow Temple, somewhere in bowels of the Freeport is the center of worship for the largest cult of The Unspeakable One. The erkunae are also known to toy with the dangerous beings in G’sho’laa’n’rr.