Ghostly Pilferer
Creature — Spirit Rogue
Whenever this creature becomes untapped, you may pay 
. If you do, draw a card.
Whenever an opponent casts a spell from anywhere other than their hand, draw a card.
Discard a card: This creature can't be blocked this turn.
Craig J Spearing
Core Set 2021 (M21)
• #52Rulings
Ghostly Pilferer's first ability triggers during your untap step, but it's put onto the stack at the same time as abilities that trigger at the beginning of your upkeep step. Even though the ability triggered first, you may order it before or after other abilities you control that are put onto the stack at this time.
(wotc • 2020-06-23)
Once Ghostly Pilferer has been blocked, activating its last ability doesn't cause it to become unblocked.
(wotc • 2020-06-23)
Players can cast spells and activate abilities after the second triggered ability resolves but before the spell that caused it to trigger does.
(wotc • 2020-06-23)
While resolving Ghostly Pilferer's first ability, you can't pay more than {2} to draw more than one card.
(wotc • 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.
(wotc • 2020-06-23)
Rulings
Ghostly Pilferer's first ability triggers during your untap step, but it's put onto the stack at the same time as abilities that trigger at the beginning of your upkeep step. Even though the ability triggered first, you may order it before or after other abilities you control that are put onto the stack at this time.
(wotc • 2020-06-23)
Once Ghostly Pilferer has been blocked, activating its last ability doesn't cause it to become unblocked.
(wotc • 2020-06-23)
Players can cast spells and activate abilities after the second triggered ability resolves but before the spell that caused it to trigger does.
(wotc • 2020-06-23)
While resolving Ghostly Pilferer's first ability, you can't pay more than {2} to draw more than one card.
(wotc • 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.
(wotc • 2020-06-23)