Leviathan, Lord of Whorls

Flash
When Leviathan, Lord of Whorls enters the battlefield, return all other nonland permanents
target player controls to their owner's hand.
{1}{u}{b}, Sacrifice another creature: Target player
puts the top three cards of their library into their graveyard. Then, if there are seven or more cards
in their graveyard, tap all creatures they control.