This spell can't be countered.

This spell costs {1} less to cast for each {W} in the mana cost of sorcery and instant spells in your graveyard.

When you play Setting of the Second Sun, if it's the second time you've casted a spell called Setting of the Second Sun this game, target player loses the game. If not, you gain 11 life and put Setting of the Second Sun into your library eleventh from the top from your graveyard.