(I'm not privileged to see the map.)
Prep Round 1:
Standard: Steel Shadows: +3 Armor AC, +3 Shield AC
Free: Drop shield
Prep Round 2:
Standard: Caul of shadows. +1 AC
Free: draw long spear.

Init: 8
AC: 26

Effects:
Caul of Shadows +1AC, Steel Shadows +3AC.

Yeah, I'll have to get that fixed. Sometimes it works.
Also, could you explain your AC to me: your sheet wasn't very explicit on the matter.

The one I gave you may be outdated. Here's a little cut from the updated version.

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Spoiler text: (Highlight or hover over the text to view)
ARMOR CLASS                               BASE ATTACK BONUS
AC Total :            22                    MELEE         RANGED
AC when Flat-Footed   18                    Total:  4     Total: +5
AC vs Touch Attack    14                    Base:  +1     Base:  +1
Base:                 10                    STR:   +3     DEX:   +4
Armor:                --                    Misc:  --     Misc:  --
Shield:               --
Dexterity:            +4                        INITIATIVE
Size:                 --                        Total:   4
Magic:                +2 Ring of Prot           DEX:    +4
Misc.:                +6 Natural Armor          Misc.:  --

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Uhg. I've noticed a few errors on the sheet since things have been tweaked. I'll send you the fixed one.

Snorting the beast feels uncomfortable in the unfamiliar setting.

Initiative: 4, you go first.

AC: 15 (touch 11)

With a great stroke of her strong wings, Aelyne immediately launched herself into the air.
http://fc01.deviantart.net/fs7...genzoman-d4l6b0x.jpg

Round 1:
  [Double Move] From B2 to N17 15'up.

Init: 8
AC: 26

Effects:
Caul of Shadows +1AC, Steel Shadows +3AC.

Final Position: N17 15'up
This message was last edited by the player at 18:58, Tue 07 May 2013.

OOC: At what altitude?

Oh sorry. 15'f. I flew pretty far, didn't have movement left to ascend higher.

With its prey approaching through the air, the hippogriff launches itself on a direct trajectory to intercept. Soaring through the air on broad wings the magical beast closes the distance fast and rather than harming the winged human, simply tries to grab it.

OOC: Initiating grapple, but need to sort out any AoO's first.

Round 1:
  [Free]
  [Move] Move to O18, 15' up
  [Standard] Charge touch attack (provokes AoO) to initiate grapple (12+2)
Status:
  Initiative: 4
  AC (Touch AC): 15 (11), currently -2

  Damage Taken: 0
  Damage Dealt: 0

Effects:

Final position: O18, 15' up

This is embarrassing. I've never once had to do a grapple check, so I don't know how they resolve.

First off, you have a long spear with 10' reach, right? You may take an AoO against the hippgriff when closing. Next, you can make an AoO against the touch attack (using claw). However, you can't make both.
Also, from a metagame perspective, you need to decide which AoO to carry out. One deals more damage, while the other may deflect the grappling attempt. In character you don't know as the hippogriff closes that it will attempt to start a grapple.

Aelyne thrust her spear at the charging Hippogriff, and the spear made contact, but that did little to alleviate her situation when the beast got it's talons on her.
Round 1 (cont):
  [AoO] Long spear - Attack: 14, Damage 11
  [Grapple] 13; Opposed grapple.
This message was last edited by the player at 18:24, Wed 08 May 2013.

OOC: The attack is a hit. The hippogriff suffers a -2 to AC from charging.
Assuming you don't damage it enough to kill it (yet) we go on with the grappling then.
The hippogriff rolls 20 on its grapple check. You need to beat that with an opposed check (BAB+STR in your case) to avoid being grappled. If you fail, we grapple and share the same space. While grappling you can cast spells that do not require a somatic component, attack with a light weapon, or natural weapon at -4 penalty, try to escape from the grapple, try to damage the opponent through grappling, and a couple of more things. I'll walk you through it.

Okay. So now I'm grappled. What happens now? Assuming I'm going to try and break the grapple. do I make an Escape Artist check?

Eventually, yes. But first you take non-lethal damage from the grapple: 8 HP

This concludes this turn.

On your turn you may try to escape using either a grapple or an escape artist check. The hippogriff is allowed an opposed grapple check.

It wasn't likely Aelyne was going to be able to overpower the beast, but it was equilly unlikely that she was going to be able to break free. She opted to try and escape.

Round 2:
 Standard: Escape artist check: 10.

Status:
 Init: 8
 AC: 26

 Damage taken: 6NL (8NL)
 Damage given: 11

Effects:
 Caul of Shadows +1AC, Steel Shadows +3AC. Fast Healing 2.

Final Position: N17 15'up

OOC: Should I list ongoing racial effects as well? (like my fast healing 2)

The magical beast continues to squeeze the winged human, trying to restrict her movement.

Round 2:
  [Free] OGC 29, grappling continues
  [Move]
  [Standard] GC to pin (22), need to beat the check or be pinned
Status:
  Initiative: 4
  AC (Touch AC): 15 (11)

  Damage Taken: 0
  Damage Dealt: 0

Effects:

Final position: O18, 15' up

And pinned she was, having not the strength to oppose the beast's might.

[GC] rolled 18.

Status:
 Init: 8
 AC: 26

 Damage taken: 6NL (8NL)
 Damage given: 11

Effects:
 Caul of Shadows +1AC, Steel Shadows +3AC. Fast Healing 2.

Final Position: N17 15'up

(OOC: So, I think I'm getting the hang of this. Is it my turn following, and I need to make a Escape or grapple check to not be pinned?")

Correct.

She was pinned, but she was far from finished. She put all her might into trying to break free.

Round 3:
 [Standard] Escape artist check: 23

Status:
 Init: 8
 AC: 26

 Damage taken: 4NL (8NL)
 Damage given: 11

Effects:
 Caul of Shadows +1AC, Steel Shadows +3AC. Fast Healing 2.

Final Position: N17 15'up

The winged human very nearly broke free, but the hippogriff manages to keep her pinned. Then it bends and twists as it tries to squeeze the air out of her body.

Round 3:
  [Free] OGC 23, but made with higher modifier, pin continues
  [Move]
  [Standard] GC to damage (24), oppose or take 8 NL damage
Status:
  Initiative: 4
  AC (Touch AC): 15 (11)

  Damage Taken: 11
  Damage Dealt: 16NL

Effects:

Final position: O18, 15' up

Aelyne was tiring, and was losing her energy trying to escape.

Round 3.5:
 [Opposed GC] 17

Round 4:
 [Standard] Escape 5.

Status:
 Init: 8
 AC: 26

 Damage taken: 10 NL (16NL)
 Damage given: 11

Effects:
 Caul of Shadows +1AC, Steel Shadows +3AC. Fast Healing 2.

Final Position: N17 15'up

Having achieved a hold the hippogriff continues to press on the attack.

Round 4:
  [Free]
  [Move]
  [Standard] GC to damage (22), oppose or take 6 NL damage
Status:
  Initiative: 4
  AC (Touch AC): 15 (11)

  Damage Taken: 11
  Damage Dealt: 22NL

Effects:

Final position: O18, 15' up

I'm just going to call it here. I'm fairly certain that I'm going to lose.
That was a good test. I know not to get grappled in the future.

Just be careful around large monsters before you get flicker online, or be sure to have some other way of getting out of grapples. Shadowcasters are unfortunately very susceptible to grapples since you always have somatic components in your mysteries.
You could have tried to hurt the hippogriff instead, using your natural weapons (and full attacking).

Oh. I didn't know I could do that. Yeah, I think I understand my weaknesses a lot better now. This was helpful.