Legendary Flying Saucer

For each opponent choose 4 permanents they
control at random. Destroy those permanents.
Then for each opponent if that player controls a creature or a planeswalker, destroy all creatures
and planeswalkers that player controls.
If that player doesn't, then if that player controls
an artifact or an enchantment, destroy all artifacts
and enchantments that player controls.
If that player doesn't, destroy all lands that player controls.