Gossamer Phantasm
Creature — Illusion
Flying
When this creature becomes the target of a spell or ability, sacrifice it.
"Belief matters more than truth. Every moment, belief in imaginary things alters lives while truth sits unnoticed and waits." —Hakim, Loreweaver
Jon Foster
Rulings
If the spell that targets Gossamer Phantasm has no other targets, it won't resolve (because it no longer has a legal target after Gossamer Phantasm has been sacrificed).
(wotc • 2021-03-19)
Gossamer Phantasm's triggered ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
(wotc • 2021-03-19)
Rulings
If the spell that targets Gossamer Phantasm has no other targets, it won't resolve (because it no longer has a legal target after Gossamer Phantasm has been sacrificed).
(wotc • 2021-03-19)
Gossamer Phantasm's triggered ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
(wotc • 2021-03-19)