When Player A uses Charm to move Player B's unit from base into a battlefield with Player C's units, who is the attacker in the resulting Showdown?

Ruling: Player B is the attacker in the Showdown between Player B and Player C, since Player B's unit contested the battlefield.

Sequence:

• Player A uses Charm on Player B's unit
• Player B's unit moves from base to a battlefield containing Player C's units
• A Showdown begins between Player B and Player C
• Player B is treated as the attacker