River Serpent can't attack unless there are five or more cards in your graveyard.
Cycling {U} ({U}, Discard this card: Draw a card.)

• Number: 66
• Rarity: C
• Power: 5
• Toughness: 5
• Type: Creature
• Subtype: Serpent
• Mana cost: 5U
• Color: Blue
• Artist: Christopher Moeller