Thrashing Mudspawn {3}{B}{B}
Creature — Beast
Whenever this creature is dealt damage, you lose that much life.
Morph {1}{B}{B} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
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Flayed Nim 89%
$0.14#24376
"Whenever this creature deals combat damage to a creature, that creature's controller loses that much life."
Archfiend of Spite 88%
$0.80#8958
"Whenever a source an opponent controls deals damage to this creature, that source's controller loses that much life unless they sacrifice that many permanents of their choice."
+1 more matching line
Nafs Asp 87%
$0.09#28687
"Whenever this creature deals damage to a player, that player loses 1 life at the beginning of their next draw step unless they pay {1} before that draw step."
Death Charmer 87%
$0.10#28469
"Whenever this creature deals combat damage to a creature, that creature's controller loses 2 life unless they pay {2}."
Glass Asp 85%
$0.17#27109
"Whenever this creature deals combat damage to a player, that player loses 2 life at the beginning of their next draw step unless they pay {2} before that step."
Vicious Battlerager 84%
$0.16#11090
"Whenever this creature becomes blocked by a creature, that creature's controller loses 5 life."