Beast of the Week: Ossagi

Last night, I got home to find my wife and son were out.  Got a call about 5 minutes later, just before I was about to call her to see where they were.  They were at a restaurant having dinner with my sister-in-law.  I headed down to the restaurant and found my son, his cousins, and the owners' kid running around being "scared" by "ossagi" [오싹이].  Asking what ossagi was, they tell me it's a ghost.  According to my son, "It comes and goes."  "From the mirror," his cousin adds. 

I'd never heard of this type of Korean ghost before, so I immediately start plying my wife and sister-in-law with questions.  The best they can tell me is that it's transparent/invisible (the word for both is the same in Korean).  And a coward.  At home, my wife sends some text messages to the sister-in-law's friend who introduced ossagi to the kids.  Turns out it's a children's book character, sorta like the Korean version of Casper the Friendly Ghost.  Only he's a scaredy-cat. 

So here's an attempt to turn Ossagi into a D&D monster. One that requires a bit more challenge than just "roll to hit, roll damage" or Clerical Turning to conquer.

Ossagi*
Armor Class: 7 (13)
Hit Dice: 2**
Move: fly 150 (50)
Attacks: 1
Damage: special
No. Appearing: 1d4 (--)
Save As: Magic-User 2
Morale: 4
Treasure Type: N+O
Alignment: Chaotic
XP: 30


Ossagi are transparent undead spirit creatures that haunt mirrors.  They are drawn to magical auras, and can drain magic items of their power, or even steal the spells from the brains of spell-casters.  Ossagi can use mirrors to travel, similar to a dimension door spell, as long as they have a mirror to enter and one to exit within 360'.  When they attack, they do no physical damage, but instead drain one magic item, chosen at random, carried by the victim of its potency.  Permanent items are unusable for 1d4 Turns.  Charged items lose 1d6 charges.  One-use items are destroyed.  A spell-caster might instead be targeted, losing one of the highest level spells memorized at random.  In any case, a Save vs. Spells is allowed to avoid the magical drain.  Ossagi are cowardly, and often flee battles.  They are Turned by Clerics as Skeletons, except they cannot be destroyed by a Turn attempt (treat all D or D+ results as T).  Adventurers who have been victims of an ossagi attack often wish to chase them down.  When they are destroyed, their bodies explode in a magical burst, recharging any items drained by the ossagi, and refreshing the memorized spells of any caster.  In addition, the mirror in which the ossagi lairs will shatter, often dropping potions and scrolls.