Invisible Stalkers

=== (A flying terror) CR 7 ===
Chaotic Any, Medium Outsider (Elemental, Extraplanar, Air)
Initiative: +8
Senses: Darkvision 60ft, Perception +12
==== DEFENSE ====
ACs: KAC: 20 EAC: 18 CMan: 28 (+4 Dex, +6/4 Natural armor, Immune to tripping)
HP: 100
Fort: +11 Ref: +11 Will: +4
Defensive Abilities Natural Invisibility; Immune Elemental Traits
==== OFFENSE ====
Speed: 30ft, Fly 30ft (Perfect)
Attack (melee): 2 Slams +12 (2D6 + 11 Kinetic (Bashing), Stun)
==== Statistics ====
STR +4 DEX +4 CON +6 INT +2 WIS +2 CHA +0
Feats: Weapon Focus (Unarmed), Improved Initiative, Lightning Reflexes, Jet Dash, Fly-By Attack
Skill: Acrobatics +14, Bluff +10, Mysticism +12, Perception +12, Sense Motive +12, Stealth +14, Survival +16; Racial Modifiers +4 to Survival 
==== Special Abilities ====
Improved Tracking (Ex): Invisible stalkers are natural trackers and hunters, and take no penalties on Survival checks when tracking and moving at any speed.
Natural Invisibility (Ex): Invisible Stalkers are perfectly invisible beings made of solidified "air" ). Invisible Stalkers also do not generate any heat, making them almost undetectable by normal, mortal means. While a spell like See Invisibility will reveal the presence of an Invisible Stalker, any other method to reveal invisibility will likely only make them slightly irritated. Against a foe which cannot pinpoint the stalker, it gains a +20 bonus to all Stealth checks when moving and a +40 when standing still.
=== Description ===
A being of "solidified air", whose body composition is closer to a mix of nitrogen, water vapour, methane and at least two supernatural materials that could not be identified, Invisible Stalkers are an uncommon "sight" in the Elemental Plane of Air. Those beings are humanoid in shape (if you can see them), about 6 feet tall but weighing only about 1 pound in total. Invisible stalkers would much rather be undisturbed and simply float on the strong winds of the upper plane, maybe finding a few practical jokes to play on other inhabitants of the Realm of Winds. The *Reason* of *Freedom* is strongly associated with them.
Sadly, most invisible stalkers are caught in the greater conflicts of reality and the elemental planes. Summoners in the Prime Material plane calls upon them for all matters of work, from acting as guardians for mystical artefacts, bodyguard duty, spying on rivals or even assassination. Almost all invisible stalkers hate to take on such tasks not because of what it implies, but because it prevents them from doing whatever they want to do. They will generally twist the words of whoever called upon them to make the job easier or shorter. The worst thing is that even in their home plane nowadays, many invisible stalkers get drafted by the Djinni to serve in their military, mainly by telling them of the horrors many other elemental creatures live under slavery by the Efreeti. Caught between a rock and a hard place (both of which are hard to find in the Plane of Air), many invisible stalkers have started looking for new places where they could reside in peace, which led a large number of them to "defect" to other planes. The sea brine doesn't trouble them too much now, and the dank and stale air of the underground is not perfect, but there are strange breezes that come from both under and over.
=== Tactics ===
Getting into a fight with an invisible stalker means one thing first: finding it. If they do not want to be seen, invisible stalkers are incredibly hard to find, combining their flight and invisibility to avoid detection. Firing at an invisible stalker is more or less useless as they generally are quickly out of the way. Invisible stalkers will generally use their Fly-by Attack feat to strike at a target then move out of the way so people cannot follow their position. 
== Tactical Stalker Detector ==
Terran military experts were rather terrified when they learned of the existence of Invisible Stalkers and Aerial Servants, which led to the scrambling for the creation of a mean of detecting them. It took a little time, money and a rather reckless technomancer to build the first Tactical Stalker Detector, which can detect trace elements of what was nicknamed "Djinnium" by some researchers. While most political buildings have at least one of these detectors nowadays, smaller version have started popping up, either as scopes that can be mounted on rifles or as goggles.
While wearing one these pieces of equipment, you count as having See Invisibility active. This hardware requires 1 charge from a battery to remain active, and can be used as a weapon scope or an armour upgrade.