Class challenge: Druid
Reward: Poison Seeds
Facing Grand Widow Faerlina, the Druid gets a special pre-made deck only for this fight. The decks are not designed to be challenging, although you could get borked if you're not paying attention. No, this fight is designed to be entertaining, and doesn't really require a special strategy to survive.
For a part of the match, it looked I was about to get crushed, until I had a chance on getting a 1/4 Gargoyle that heals itself at the end of the turn, and Marked it a bit, so that nothing could go through to it, since Faerlina doesn't have any direct removal.
The deck contained some Nerubian Eggs, and I even ended up with a pair of Poison Seeds, but I never actually had a chance to play with them.
Poison Seeds (4-mana) destroys all minions and replaces them with 2/2 treants. I can see this as an exceptionally effective AOE, especially since the Druid isn't known able to handle big creatures like Ragnaros, Ysera or any of the Giants.
Class challenge: Rogue
Reward: Anub’ar Ambusher
Then we have the Rogue Challence, who faces the Giant Spider again, Maexxna. Her hero power actually works for the player, since it actually helps with possible combos. They're not many, but that extra damage from the SI:7 Agent is always welcome. However, in the mid-game she always focused her Web on a single Anub'ar Ambushar, whilst ignoring the extensive line-up of creatures I had prepared there.
Overall, the Ambusher, a 4mana 5/5 is a seriously able creature. Its downside, the 'return a random friendly minion to your hand' can actually work in your favor, especially if you are a rogue that relies on combos and battlecries. It's not the best way to bounce, but given a bit of foresight, and it bounces like none other.