Board Thread:Wiki General Discussion/@comment-6053607-20130124214919/@comment-5706972-20130125210327

Yes, Winter is untradeable. What you do with it is up to you.

Untradeable cards include:

Referral cards:   (Seed) Sylvain of Jade Woodlands, (Calm) Temperance Scorch Dragon,  (Imprison) Imprisoned Battle Dragon, (Carefree) Vagabond Hydro Dragon

Friend Invitation cards: White Drake of Evil Bane

Login Bonus cards: Winter, Evocative Magician, (Breeze) Whimsical Tempest Queen

Facebook Post cards: Starcaller Dragon, Blundering Dragon Zombie, Diamond Dust Vampyre

...And basically any card that is given for free...