Winter's Chill

Cast only during combat before defense is chosen. At end of combat, destroy X target attacking creatures; X cannot be greater than the number of snow-covered lands you control. For each attacking creature, its controller may pay o1 or o2 to prevent it from being destroyed in this way. If that player pays o1, the creature neither deals nor receives damage in combat. If that player pays o2, the creature deals and receives damage in combat as normal.