Omnath, Locus of Destruction

When Omnath, Locus of Destruction enters the battlefield, each opponent discards a card.
Landfall — Whenever a land enters the
battlefield under your control, each opponent
loses 4 life if this is the first time this ability has resolved this turn. If it's the second time, each opponent sacrifices a land. If it's the third time,
Omnath deals 4 damage to each creature and
each planeswalker you don's control.