2020-06-23 : Griffin Aerie's ability looks at how much life you've gained in the turn, even if it wasn't on the battlefield when you gained life. It doesn't care if you also lost life, even if you lost more life than you gained.

2020-06-23 : If you haven't gained 3 life by the time your end step begins, Griffin Aerie's ability won't trigger at all.

2020-06-23 : You create just one Griffin token, no matter how much life you've gained past 3 life.