2020-04-17 : 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.

2020-04-17 : If an effect allows you to cast a spell “as though” it has flash, Slitherwisp’s last ability won’t trigger.

2020-04-17 : In a Two-Headed Giant game, Slitherwisp’s last ability causes the opposing team to lose 2 life and you to draw one card.

2020-04-17 : Players can cast spells and activate abilities after the triggered ability resolves but before the spell that caused it to trigger does.