Chambered Nautilus {2}{U}
Creature — Nautilus Beast
Whenever this creature becomes blocked, you may draw a card.
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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.
Nessian Boar 89%
$0.32#12784
"Whenever this creature becomes blocked by a creature, that creature's controller draws a card."
Cactarantula 84%
$0.06#15583
"Whenever this creature becomes the target of a spell or ability an opponent controls, you may draw a card."
Tenured Concocter 84%
$0.07#26279
"Whenever this creature becomes the target of a spell or ability an opponent controls, you may draw a card."