River Serpent {5}{U}
Creature — Serpent
This creature can't attack unless there are five or more cards in your graveyard.
Cycling {U} ({U}, Discard this card: 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.
Deep-Sea Terror 98%
$0.18#27299
"This creature can't attack unless there are seven or more cards in your graveyard."
Vantress Gargoyle 96%
$0.32#11501
"This creature can't attack unless defending player has seven or more cards in their graveyard."
Bloodcrazed Goblin 91%
$0.18#25197
"This creature can't attack unless an opponent has been dealt damage this turn."
Goblin Cohort 91%
$0.24#24308
"This creature can't attack unless you've cast a creature spell this turn."
Mogg Conscripts 91%
#27105
"This creature can't attack unless you've cast a creature spell this turn."
Harbor Serpent 91%
$0.14#20206
"This creature can't attack unless there are five or more Islands on the battlefield."
Orcish Conscripts 90%
#30294
"This creature can't attack unless at least two other creatures attack."
Silburlind Snapper 89%
$0.04#26997
"This creature can't attack unless you've cast a noncreature spell this turn."
Warden of the Chained 87%
$0.10#27889
"This creature can't attack unless you control another creature with power 4 or greater."
Lambholt Pacifist // Lambholt Butcher 87%
$0.21#23485
"This creature can't attack unless you control a creature with power 4 or greater."
Mogg Toady 87%
$0.11#30572
"This creature can't attack unless you control more creatures than defending player."
Goblin Goon 87%
$0.35#20282
"This creature can't attack unless you control more creatures than defending player."