When you play an ~13 Mana battle, you'll typically see Thaddius Brood chosen. This is what both me and my competitor chose.
Your tank is always the Cursed Windeku, and that's what the both of us chose too.
I usually choose the Undead Badger as my next monster, as it has sneak, but I learned from my mistake... this monster is NOT the best choice.
The best choice is the Crypt Beetle.
While the Crypt Beetle can't attack, unless in the tank position, it has the Shield ability. The Undead Badger will do 0 damage to my monster, and once in the tank position, my Crypt Beetle will lay waste to the Undead Badger.
Just remember, this strategy usually works in ~13 Mana battles. Enjoy.