Thornmantle Striker 

Creature — Elf Rogue
When this creature enters, choose one —
• Remove X counters from target permanent, where X is the number of Elves you control.
• Target creature an opponent controls gets -X/-X until end of turn, where X is the number of Elves you control.
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.
Cemetery Desecrator 95%
$0.34#17330
"• Target creature an opponent controls gets -X/-X until end of turn, where X is the mana value of the exiled card."
+1 more matching line
Shambling Ghast 93%
$0.43#3264
"• Target creature an opponent controls gets -1/-1 until end of turn."
Downwind Ambusher 93%
$0.15#20063
"• Target creature an opponent controls gets -1/-1 until end of turn."
+2 more matching lines
Wail of War 81%
$0.16#14312
"• Creatures target opponent controls get -1/-1 until end of turn."
+1 more matching line