Thunderous Cataclysm

When you cast Thunderous Cataclysm from
your hand, exile it. At the beginning of your
next upkeep, play Thunderous Cataclysm from
exile without paying its mana cost, then exile it.
Thunderous Cataclysm can't be countered.
Each player exiles the top half of their library,
loses half their life total, and chooses half of
the permanents they control, then exiles them.
Round down each time.