Seething SpiritCreature 11
Source Pathfinder Bestiary 3
Perception +15 (darkvision, tastes anger (imprecise) 1 mile)
Languages Common, Dwarven, Jotun, Tongues
Skills Acrobatics +21, Deception +20, Diplomacy +-5, Intimidation +24, Stealth +21
Str -5, Dex +6, Con +0, Int +2, Wis -2, Cha +7
AC 29; Fort +17; Reflex +23; Will +21;
HP 145 (negative healing)
Speed 0 feet (fly 40 feet)
Immunities death effects, disease, paralyzed, poison, precision, unconscious
Weaknesses Emotion 12
Resistances All 10
Ephemeral Claw
+22 (+17, +12) to hit (evocation, occult) 3d12+7 SlashingDarkvision
A monster with darkvision can see perfectly well in areas of darkness and dim light, though such vision is in black and white only. Some forms of magical darkness, such as a 4th-level Darkness spell, block normal darkvision. A monster with Greater Darkvision, however, can see through even these forms of magical darkness.
Taste Anger (Imprecise) 1 mile (detection, divination, occult)The spirit can taste anger and hatred from creatures experiencing those emotions within 1 mile (imprecise).
At-Will SpellsThe monster can cast its at-will spells any number of times without using up spell slots.
Constant SpellsA constant spell affects the monster without the monster needing to cast it, and its duration is unlimited. If a constant spell gets counteracted, the monster can reactivate it by spending the normal spellcasting actions the spell requires.
Negative HealingA creature with negative healing draws health from negative energy rather than positive energy. It is damaged by positive damage and is not healed by positive healing effects. It does not take negative damage, and it is healed by negative effects that heal undead.
Pulse of Rage (aura, emotion, enchantment, mental, occult)20 feet Aura
This aura emanates from any creature possessed by the seething spirit, and it's inactive while the spirit isn't possessing anyone.
Any creature in the aura, including a creature possessed by the spirit, takes a -1 status penalty to AC, can't perform actions with the concentrate trait except for the Seek action and actions with the rage trait, and gains a +2 status bonus to melee damage rolls against the spirit's enemies.
A creature can attempt a DC 30 will save when it enters the aura to avoid the effect. If the creature would need to attempt a save against the aura again within 24 hours, it automatically uses the same save result rather than attempting a new save.
Effect: Pulse of Rage
Vulnerable to Calm EmotionsA seething spirit can't attempt to possess a creature affected by Calm Emotions. If creature possessed by a seething spirit fails a saving throw against calm emotions, the spirit is forced out.
If the spirit isn't possessing a creature and is targeted with calm emotions, the spirit takes 12Furious Possession 
The seething spirit attempts to possess an adjacent corporeal creature. This has the same effect as a Possession spell (DC 30 will), except since the spirit doesn't have a physical body, they're not Unconscious and Paralyzed when the effect ends. The spirit can't Dismiss the possession.
The creature gains 12 temporary Hit Points that are lost when the possession ends. During the possession, the creature has the pulse of rage aura. Each time the possessed creature makes a melee Strike, the spirit can substitute their ephemeral claw attack modifier, damage amount, or both in place of the creature's own statistics.
Occult Innate Spells (DC 32, +24 to hit)
1st Level: Ventriloquism (At Will)
2nd Level: Invisibility (At Will) (Self Only), Paranoia, Remove Fear
3rd Level: Mind Reading (At Will)
4th Level: Suggestion
5th Level: Tongues (Constant)
Hatred so powerful it lives beyond the grave-this sentiment animates the ephemeral crimson apparitions known as seething spirits. Single-minded in nature, they stoke the fires of anger and hate, capable of planning and strategy, but the one thing beyond their grasp is personal growth. Though similar to ghosts, seething spirits retain much less of their former living selves. Most of their soul has moved on, and only the fury remains. There's no way to set a seething spirit to rest: only violence can destroy it.
By possessing a creature and nurturing the seeds of resentment and rage already within its mind, a seething spirit can greatly alter the host's behavior and personality. When broached about such changes, a host might claim they're just finally "telling it like it is." Because a seething spirit can't voluntarily end its possession, it's essentially one with its victim until the victim's rage results in death. A seething spirit doesn't take pleasure in this death-they rapidly move on in search of a new rageful host.
Traits
Something of uncommon rarity requires special training or comes from a particular culture or part of the world. Some character choices give access to uncommon options, and the GM can choose to allow access for anyone. Less is known about uncommon creatures than common creatures. They typically can't be summoned. The DC of Recall Knowledge checks related to these creature is increased by 2.
IncorporealAn incorporeal creature or object has no physical form. It can pass through solid objects, including walls. When inside an object, an incorporeal creature can't perceive, attack, or interact with anything outside the object, and if it starts its turn in an object, it is slowed 1. Corporeal creatures can pass through an incorporeal creature, but they can't end their movement in its space. An incorporeal creature can't attempt Strength-based checks against physical creatures or objects-only against incorporeal ones-unless those objects have the ghost touch property rune. Likewise, a corporeal creature can't attempt Strength-based checks against incorporeal creatures or objects. Incorporeal creatures usually have immunity to effects or conditions that require a physical body, like disease, poison, and precision damage. They usually have resistance against all damage (except force damage and damage from Strikes with the ghost touch property rune), with double the resistance against non-magical damage.