Monstrous Monday: Frost Maiden

Woke up to freezing fog this morning.  That sounds totally made-up, but there is a thin sheet of ice everywhere.  Remind me again WHY I live in Chicago?

Today's little beastie is another one from the upcoming Winter Witch book.  It should feel familiar to any old-school gamer.

Frost Maiden
Hit Dice: 10
Armor Class: 3 [17]
Attack: Spell abilities or two fists (2d8x2) (giant size)
Saving Throw: 8
Special: Spell-like abilities, growth, immune to all cold.
Movement: 18 (can run without impediment over snow and ice)
Alignment: Chaotic
Number Encountered: 1
Challenge Level/XP: 12/2,000
Frost Maidens are related to both Frost Giants and Snow Elves.  It is believed that the first Frost Maiden was the offspring of a snow elf princess who was abducted by a Frost Giant Jarl.  The Princess was a powerful winter witch and she cursed her abductor and his family.  Now once every 100 or so births among frost giants will result in a frost maiden.  Due to the curse, the frost giants cannot abandon their frost maiden daughters and they usually rise to levels of importance and power.
These creatures stand some 5’ tall under normal conditions. Her skin is an unhealthy white or pale blue with white or platinum blonde hair. Their eyes are a piercing ice blue. They appear as a snow elf, but something is different about them.  They are unearthly beautiful with melodious voices and a coquettish smile. The often will appear wearing only the barest minimum to support modesty, but little else.  They are often barefoot.
Frost Maiden are all irredeemably evil. Their favorite game is to tease human males to point they are maddened with lust then they lead them to their deaths.  Usually in a blind canyon where they will bury them in an avalanche or trap them in a deep bit of ice.  They are also not above leading them into ambushes of winter wolves, worgs, or their frost giant brothers.   Some males they trick into acts of passion.  The resulting children are the same race as the father. Children of these unions have an additional +1 to saves against cold-based attacks.
The frost maiden can cast spells as a 7th level winter witch and can also once per day grow to three times her size (15’) to the size of a frost giant once per day.  She will revert to her normal size at sunrise.
Some sages say that the “snow elf princess” was actually the Snow Queen, the Faerie Lady of Ice and Snow and the “frost giant jarl” was no less a personage than Thrym, lord of the Frost Giants.  This is unconfirmed and both the Snow Queen and Thrym are loathe to discuss it. But it is known that many frost maidens serve the Snow Queen in her court.

I used this monster as a "side quest" after running G2 Glacial Rift of the Frost Giant Jarl.  The ice maiden in question was the daughter of the Jarl.  My players were quite surprised when the "snow elf" they were chasing starting using spells and became a 15' frost giant.