Regigigas, Locus of Creation

When Omnath, Locus of Creation enters the battlefield, draw a card.
Landfall — Whenever a land enters the battlefield under your control, you gain 4 life
if this is the first time this ability has resolved this turn. If it's the second time, add {r}{g}{w}{u}. If it's the third time, Omnath deals
4 damage to each opponent and each planeswalker you don't control.