n medium air elemental 

Perception +16; darkvision

Languages Auran

Skills Acrobatics +16, Stealth +18, Survival +15 (+19 to Track)

Str +3 Dex +6 Con +3 Int -2 Wis +2 Cha +0

AC  26; Fort +14, Ref +18, Will +11

HP 70; Immunities bleed, poison, paralyzed, sleep

Naturally Invisible The invisible stalker is invisible at all times, though when it takes a hostile action of any kind, it is hidden instead of undetected until the start of its next turn, as the vague outline of its humanoid form is faintly visible for a short period of time.

Speed 25 feet, fly 25 feet

Melee [>] fist +18 (agile, finesse), Damage 1d10+5 bludgeoning

Sneak Attack The invisible stalker deals 2d6 extra precision damage to flat-footed creatures.

Swift Tracker The invisible stalker moves at full Speed while Tracking.

Bestiary, page 144. Expanded in LOIL.