Master of Cruelties {3}{B}{R}
Creature — Demon
First strike, deathtouch
This creature can only attack alone.
Whenever this creature attacks a player and isn't blocked, that player's life total becomes 1. This creature assigns no combat damage this combat.
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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.
Slithering Shade 88%
$0.08#28698
"This creature can attack as though it didn't have defender as long as you have no cards in hand."
Ogre Jailbreaker 88%
$0.03#27254
"This creature can attack as though it didn't have defender as long as you control a Gate."
Geist of the Lonely Vigil 87%
$0.12#28971
"This creature can attack as though it didn't have defender as long as there are four or more card types among cards in your graveyard."
Chaos Lord 82%
$0.52#26305
"This creature can attack as though it had haste unless it entered this turn."
+1 more matching line
Goblin Cohort 80%
$0.24#24308
"This creature can't attack unless you've cast a creature spell this turn."
Mogg Conscripts 80%
#27105
"This creature can't attack unless you've cast a creature spell this turn."