Will-o'-Wisp

Creature 6

Small
aberration
air

Perception: +16; darkvision
Languages: Aklo, Common
Skills: Acrobatics +18, Deception +12, Intimidation +12, Stealth +16; Str −5, Dex +6, Con +0, Int +2, Wis +4, Cha +2

AC: 27; Fort +10, Ref +16, Will +14
HP: 50

Glow (aura, light) 20 feet.

A will-o'-wisp is itself naturally invisible, but glows with a colored light, casting bright light in the aura and making it visible.

Magic Immunity A will-o'-wisp is immune to all spells except Force Barrage, Quandary, and Revealing Light.

Speed: 0 feet, fly 50 feet

Melee ◆ shock +17 (electricity, magical), Damage 2d8+4 electricity

Feed on Fear ◆ (concentrate) Frequency once per round

Requirements An enemy within 15 feet is under a fear effect or Dying

Effect The will-o'-wisp feeds on the creature's terror. It regains 2d4 healing Hit Points, and if it has Gone Dark, its glow reignites.

Go Dark ◆ (concentrate) The will-o'-wisp extinguishes its glow, becoming Invisible. It can end this effect with another use of this action. If it uses its shock attack while invisible, the arc of electricity lets any observer determine its location, making the will-o'-wisp only Hidden to all observers until it moves.

Source: Pathfinder Monster Core

Running this fight? Add the will-o'-wisp 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.