When River Ampitheater enters the battlefield, sacrifice it unless you pay .
: Add or to your mana pool. River Ampitheater deals 1 damage to you.
: River Ampitheater becomes a 2/1 blue and red Cephalid creature until end of turn. It's still a land.
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: Add 
or to your mana pool. River Ampitheater deals 1 damage to you.: River Ampitheater becomes a 2/1 blue and red Cephalid creature until end of turn. It's still a land.
