Forged in the Barrens Cards List & Guide
PassiveYour Hero Power is upgraded and costs (1).
Shaman becomes "(1): Summon a (basic) Totem of your choice" - it also let you summon more than once the same basic totem
The abilities that come from Justicar Trueheart: http://www.hearthpwn.com/cards/22276-justicar-trueheart
Thanks! I was going to make a post that compiled them all in a list to help us all out, but looks like I don't have to.
Hunter becomes "(1): Deal 3 damage to the enemy hero"
When your heropower is upgraded (dk etc) it still costs 1, the other effect like extra dmg may be lost
Rogue becomes "(1): Equip a 2/2 weapon"
Druid is "(1): +2 attack, +2 armor"
Warlock becomes "(1): Draw a card."