An ability that triggers when a player casts a spell resolves before the spell that caused it to trigger, but after targets have been chosen for that spell. It resolves even if that spell is countered.
19-03-2021
wotc
Because it's not on the battlefield yet, casting Sigil of the Empty Throne won't cause its own ability to trigger.
Random a card of Magic: The Gathering (MTG), but you can also roll the D20 dice, random a Planeswalker, have fun with the random rules and more.