Then River Song deals damage to that player equal to its power. Being able to make River Song stronger when players mess with their deck is one thing, but being able to also hurt players for doing so is excellent
Happy brewing!
For example, if you control Fated Firepower with two fire counters on it, attack with a 5/5 creature with trample, and your opponent blocks with a 2/2 creature, you can assign 2 damage to the blocker and 3 damage to the defending player
P/T Number 309 Language English Legal Formats Commander, Historic, Legacy, Modern, Vintage Not Legal Formats Alchemy, Brawl, Competitive Brawl, Pauper, Pioneer, Standard, Timeless Rulings (3/19/2021) If for some reason you can't win the game (because your opponent has cast Angel's Grace this turn, for example), you won't lose for having tried to draw a card from a library with no cards in it