2020-06-23 : An ability that triggers when a player casts a spell resolves before the spell that caused it to trigger. It resolves even if that spell is countered.

2020-06-23 : If the chosen target is an illegal target by the time Rin and Seri's last ability tries to resolve, the ability won't resolve. You won't gain life.

2020-06-23 : Rin and Seri's first two abilities don't trigger when you cast Rin and Seri.

2020-06-23 : The amount of damage Rin and Seri's last ability deals is determined only as that ability resolves. If Rin and Seri is still on the battlefield, it'll count itself.