For each triggered ability, the game checks to see if the condition is true at the moment the ability would trigger. If the condition isn't true, the ability won't trigger. If the ability does trigger, the game will check again to see if the condition is true as the ability tries to resolve. If it's not true at that time, the ability won't do anything.
2016-01-22
In a multiplayer game, it's possible for the condition to be true at both times but with respect to two different opponents.
Flying
When Linvala enters, if an opponent has more life than you, you gain 5 life.
When Linvala enters, if an opponent controls more creatures than you, create a 3/3 white Angel creature token with flying.
