Heedless One 

Creature — Elf Avatar
Trample
Heedless One's power and toughness are each equal to the number of Elves on the battlefield.
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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.
Doubtless One 82%
$0.21#21188
"this card's power and toughness are each equal to the number of Clerics on the battlefield."
Plague Rats 82%
$0.16#25802
"this card's power and toughness are each equal to the number of creatures named this card on the battlefield."
Altar Golem 81%
$0.50#20213
"this card's power and toughness are each equal to the number of creatures on the battlefield."
+1 more matching line
Beast of Burden 81%
$0.53#17441
"this card's power and toughness are each equal to the number of creatures on the battlefield."
Ixidron 80%
$0.37#7683
"this card's power and toughness are each equal to the number of face-down creatures on the battlefield."
Caller of the Hunt 80%
$1.26#21197
"this card's power and toughness are each equal to the number of creatures of the chosen type on the battlefield."