Mergo, The Traveling Merchant

At the beginning of your second main phase
reveal your hand. Bid (Each player may cast spells
from among the revealed cards by paying mana of
any color. If casting of the same spell from different
players occur, they must bid off more mana
than the other player to cast it). If a player
casts a spell you own, create treasure tokens
equal to the spells converted mana cost.
Black Market - Pay 10 Treasures:
Transform Mergo, Traveling Merchant.