Thundering Mightmare {4}{G}
Creature — Horse Spirit
Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as Thundering Mightmare is paired with another creature, each of those creatures has "Whenever an opponent casts a spell, put a +1/+1 counter on this creature."
click a line to search just that ability, click more to combine them
Cards that do something similar expected a card that isn't here?
Reports become test cases the matcher is graded against before an update ships. Delvefall isn't a chatbot guessing, it compares the printed rules text of every card with plain math, and examples like yours decide which differences should count.
Taurean Mauler 83%
$0.72#940
"Whenever an opponent casts a spell, you may put a +1/+1 counter on this creature."
Brineborn Cutthroat 81%
$0.23#10382
"Whenever you cast a spell during an opponent's turn, put a +1/+1 counter on this creature."