Omnath, Locus of Courage

Convoke, Flash
When Omnath, Locus of Courage enters the battlefield, choose one that hasn't been chosen this turn,
• Creatures you control gain +7/+7 and Trample Until the end of the turn
• Create a Green and White Elemental token with power and toughness is equal to the number of creatures you control.
• Gain life equal to the total toughness of creatures you control.