Ever played hide 'n seek with some air?

Quote Originally Posted by Rasharuach
A cloud that resembles dense smoke curls against the shadows of the building, whirling silently like a wheel. The impression of eyes are visible from a moment, but the cloud is quite large - Well over thirty feet. It leers at you for a moment and then hurtles towards you, a sideways tornado reaching out for you.
Rasharuach was born in the darkest corner of the plane of air and resembles nothing more than a dark storm cloud. She had a life before he became the keeper of the gate, but that was an eternity ago. Rasha was chosen for her devotion to a particular god of darkness and bound by divine agreement as a guardian after the gods couldn't settle on what to do about the gate a group of dead cloud giants. Gods on favorable terms with the heavenly hosts wanted it salvaged and employed. Gods with unfavorable relations wanted it destroyed. Rather than initiating crusades and holy wars, the gods agreed to set watchers of comparable gifting. The good made the dawnbirds, summoned automatically every day from heaven, to give advice to any brave heroes and the wicked called up Rasha to kill them and bent her into something even more twisted.

Rasharuach has born the past few thousand years with relative genius and serenity. Still, she now has a terrible nervous tick of pacing incessantly - Rasha is never still, always darting up and down the halls and walls of the castle, spinning in the air, looping around the outer boundaries he is bound to (the walls of the castle). She is forbidden from damaging original parts of the castle, but she likes to move her kills' bodies around in exciting ways as displays. She also amuses herself by killing dawnbirds every morning. In theory, Rasharuach should probably spend most of his days lurking right around the research room. Rasha isn't even sure that the god she worships still exists. She's insanely old and has spent most of her eternity alone. She mostly doesn't fight it, but she isn't perfectly responsible.

Rasha is incredibly powerful, cruel, and somewhat unbalanced. She's not terribly worried about being killed, but she is afraid of mind control and tries to kill casters as quickly as possible accordingly.

The Crashed Castle:
The mountain of Castlecrown has an enormous castle jutting forth from near the peak where it resembles a wreck ship, a series of spires and walls with various levels of damage. If you rise at dawn, you can see a thousand golden stars sparkle and then watch a black cloud snuff them out in rapid succession.
There is a great, half-collapsed cloud castle jammed into Castlecrown Mountain near the peak from the age of giants. Cyclopean in stature, the massive castle's original inhabitants were holy cloud giants who had discovered how to open a gate into heaven permanently. Another band of cloud giants stopped them and the castle crashed into the mountain. The gods of good set mystic runes into the castle to summon dawnbirds* each morning and the gods of evil commissioned Rasharuach to protect it.

The castle's interior design was originally spartan like monastery with non-iconographic patterns and the flowing script of celestial etched into the stone, holy texts and implements, magical devices, and great open windows that enabled the cloud giant to contemplate nature. It's outer courts held great trees and magnificent walls.

Now, the walls of the courtyard are shattered and the state of the inner parts of the castle are varied, from nearly unchanged except for the bodies to utterly unrecognizable. Floors and roofs have fallen in on some rooms. Bodies, of the original cloud giants and of later adventurers (of every size, stripe, and sort) killed by Rasharuach, litter the castle. Holed are knocked, gouged, and toppled over in inner and outer walls and piles of horse sized stones lie in and out of rooms, corridors. A tower might have fallen, if it suits your purposes. Everything is scaled to the cloud giants that once filled the castle and thus likely to render the human sized adventurers rather small.

The gate, or its activating skeleton, is in a central tower that stands unbelievably tall. It is incredibly light, incredibly large, being about fifteen pounds and thirteen feet tall A great, spiraling staircase reaches the research room, which has been locked shut for centuries.

*The dawnbirds are effectively summoned Celestial Ravens with the ability to speak Celestial and Giant and permanent Daylight spells cast on them, designed to allow exposition if you prefer it to be available, but also because I like the image of birds made of golden daylight blooming across the castle at the first light of the sun. They're not necessary exactly, but I felt they added color.

Build Stub and Table:
Dark (Cormyr Tearing of the Weave, Pg. 152) Corrupted (Book of Vile Darkness) Air Elemental 44
Base Stats: STR 12, DEX 13, CON 10, INT 14, WIS 15, CHA 8
Elemental: 24, 35, 18, 14, 15, 8
Corrupted: 28, 33, 22, 14, 13, 6
CR 16: WIS +1
CR 17-20: DEX +3
CR Class Base Attack Bonus Fort Save Ref Save Will Save Skills Feats Class Features
12 Dark Air Elemental, 24l +18 +8 +14 +8 Hide 27, Move Silently 27, Listen 27, Spot 27 Combat Expertise, Improved Trip, Knock-down, Power Attack, Combat Reflexes, Dodge, Mobility, Flyby Attack, Great Flyby Attack [SS35], Weapon Finesse(b), Improved Iniative (b) Whirlwind, Elemental Traits,air Mastery, Hide in Plain Sight, Hide +8, Move Silently +6, DR 10/-, Cold Resistance 10
15 Corrupted Template +18 +8 +14 +8 Hide 27, Move Silently 27, Listen 27, Spot 27 - Slam 3d8, Fast Healing 10, Disruptive Attack 12, Acid Immunity.
16 Aberration 4 +21 +9 +15 +12 Hide 31, Move Silently 31, Listen 31, Spot 31 Improved Natural Attack Disruptive Attack 14
17 Aberration 8 +24 +10 +16 +14 Hide 35, Move Silently 35, Listen 35, Spot 35 Improved Flyby Attack Disruptive Attack 16
18 Aberration 12 +27 +12 +18 +16 Hide 39, Move Silently 39, Listen 39, Spot 39 Cleave, Great Cleave Disruptive Attack 18
19 Aberation 16 +30 +13 +19 +18 Hide 43, Move Silently 43, Listen 43, Spot 43 Great Fortitude Disruptive Attack 20
20 Aberration 20 +33 +15 +20 +20 Hide 47, Move Silently 47, Listen 47, Spot 47 Alertness, Iron Will

Tactics and Build Discussion:
Rasharuach is an ambush oriented character. She is usually hidden and uses Great Flyby Attack after lining herself up ideally, hitting up to 12 opponents that can be lined up within a hundred ten foot long, 35 feet wide lane (she flies over the opponents). She then automatically triggers Knock-down and rolls a trip attack (which almost always succeeds, and note that a creature need not be on land to be tripped). If that works, she gets another attack on the tripped target. After that, she either bolts to set up another ambush (if the research room is distant) or she turns around for another go (if it's close.). At higher levels, she remains hidden and silent throughout.

Ideal CR and CR 15 & 20
Rasharuach at CR 15 is a frightening combat monstrosity (Able to attack the whole party, average damage 60ish per opponent, fast healing 10) and a threatening stealth presence. (+40 to Hide/+46 to Move Silently) She can be a party killer if she's playing it smart, though after so many years, she has something of an inclination to play with her prey. She has excellent spot and listen.

Rasharuach's ideal CR is sixteen, where she benefits from a strong Will save and her damage is still high for an on level monster (4d8+9+12 for thirty eight per level without power attack. Usually two attacks.) She's quiet stealthy at this level. Her observational powers are also quite good, with a solid +13 against invisible opponents and a +31 to hear.

At CR 20, Rasharuach is basically invisible, since she can easily take the -20 to her Move Silently/Hide check from running/attacking (+40 to hide).