Durable. Skirmisher. Banish.
Replace 4 non-rares in opponent's hand with Durable or Charge uncom/rares.
Tower: +2N
N = #Charge X #Durable cards in opponent's hand.
When played, this potentially upgrades commons from opponent's hand, though only to charge/durable cards. Max tower gain is 4x4 cards in opponent's hand, giving Tower: +32. The chance of this occurring is very low, however. If opponent has no charge/durable cards, playing this will give them one of the following:
4 charge / 0 durable, for 0 tower gain
3/1 for 6 tower gain
2/2 for 8 tower gain
Afterward, opponent will lose a charge and durable card to skirmisher/banish effect (giving you resources), making it:
3/0
2/0
1/1
So it is only on the second turn playing this rare that it starts to give respectable amounts of tower. When played multiple times in a row, it can do very good tower gain, but multiple plays of the card will give the opponent a lot of different rares to use against you.