Journey to Ungoro Guide
Whenever your opponent plays a Rare card, gain +1/+1.
In the boss fight for Arch Thief Rafaam, he steals your deck.You receive a 'spare' deck to use which has atleast two of these cards.
Therefore, you can prioritize building your (HIS) deck to contain bad rare cards; weakening his plays and empowering your weapon.HOWEVER, he also has a card that steals your weapon! Luckily your deck has Harrison Jones!