Aerial Servant1
A faint ripple in the air suggests a hazy and vaguely humanoid vapor moving with terrible swiftness.

Aerial Servant (CR 11; XP 12,800)
Medium outsider (elemental)
Init +10; Senses darkvision 60 ft.; Notice +16
AC 23, flat-footed 17
(+6 Dex, +7 natural)
hp 149 (13d10+78)
Fort +10, Ref +14, Will +10
DR 10/magic; Defensive Abilities natural invisibility; Immune elemental traits
Speed fly 60 ft.
Melee 2 slams +19 (2d8+6 plus grab)
Special Attacks constrict (2d8+6), smother, sneak attack +2d6, wind blast
Str 23, Dex 22, Con 23, Int 4, Wis 10, Cha 11
Base Atk +13; CMB +19 (+23 grapple); CMD 35
Feats Combat Reflexes, Following Step, Improved Initiative, Iron Will, Power Attack, Step Up, Step Up and Strike
Skills Knowledge (planes) +13, Perception +16, Stealth +19, Survival +14 (+24 to track); Racial Modifiers +4 Survival
Languages Auran, Common
SQ improved tracking
Environment planes (Realms Within)
Organization solitary
Treasure none
Special Abilities
Improved Tracking (Ex) An aerial servant takes no penalty on Survival checks when moving its full speed and gains a +10 bonus on Survival checks to track.
Natural Invisibility (Su) This ability is constantly in effect, even when the aerial servant is attacking, and is not subject to invisibility purge. Against foes that are unable to see invisible creatures, it gains an additional +20 bonus on Stealth checks when moving, or +40 when stationary. On the Astral Plane or the Ethereal Plane, an aerial servant gains concealment (20% miss chance) rather than invisibility.
Wind Blast (Su) Once every 1d4 rounds, as a standard action, an aerial servant can release a blast of wind in an 80-foot line, dealing 8d8 points of bludgeoning damage (Reflex DC 22 half). Medium or smaller creatures that fail their saving throws are knocked prone and pushed 1d4 × 5 feet away. The save DC is Constitution-based.

Aerial servants are deadly hunters native to the Plane of Air, though they often wander through planar portals to the Ethereal Plane and sometimes roam the Astral Plane as well. They are generally called to the Material Plane as bounty hunters or assassins, using their natural invisibility and near-faultless tracking skills to pursue their quarry and then strike unseen. They typically scatter enemies with blasts of wind before closing in to strangle their prey. While an aerial servant is easy to confuse with an invisible stalker, the former is far more dangerous, and those who misidentify the creature may not live to regret underestimating it.

Those who call aerial servants must be careful to assign them tasks that are possible for them to complete, as the temperamental elementals occasionally track down and attack their callers if they fail at their assigned tasks.