Welcome to #CMAskTheJudge! This time we want to know what happens when Ancient Greenwarden doubles Omnath, Locus of Creation's landfall trigger. Comment on our video (or below) with your answer and then check whether you got it right or wrong!
You will get the first (gaining 4 life) and second (generating four mana) bonus. Ancient Greenwarden doubles the triggered ability, so you put two instances of Omnath's ability onto the stack. Each instance resolves separately, and the ability only checks how many times it already resolved upon resolution, not as it triggers. Note: If you put a second land onto the battlefield, you only get the third bonus (4 damage to each opponent and planeswalker you don't control) and nothing else.