Kraxon, Scourge of Knights

Flying, haste
Groundbreaker ({0}: This creature loses flying until
end of turn and cannot be blocked this turn. Use this ability only once per game)
Whenever Kraxon, Scourge of Knights attacks
and isn't blocked you may pay {x}{r/w} if you do,
Kraxon, Scourge of Knights deals X damage to
each opponent.