Hearthpwn

Give your opponent a taste of their own medicine. 

50-ish games in and these are the results so far:

List of decks this counters:

• Refreshing Spring Water/Incanter's Flow/[Insert Damage Spell here] Mage
• Mill Druid
• Most "Fun" decks (but in a fun way!)

Decks that it goes about even with:

• Snowfury Giant Shaman - Depends on how hard they go off before you can get Hysterias going.

List of decks this has trouble beating

• Pogo-Hoppers - ...unless they go all out and then Hysteria can win you the game. Otherwise, fish for answers with Palm Reading.
• Edwin VanCleef - Usually too big too quick to answer.