Epistolary Librarian {2}{W}{U}
Creature — Astartes Wizard
Veil of Time — Whenever this creature attacks, you may cast a spell with mana value X or less from your hand without paying its mana cost, where X is the number of attacking creatures.
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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.
Kinscaer Sentry 86%
$0.46#8303
"Whenever this creature attacks, you may put a creature card with mana value X or less from your hand onto the battlefield tapped and attacking, where X is the number of attacking creatures you control."
Surtland Elementalist 83%
$0.24#16853
"Whenever this creature attacks, you may cast an instant or sorcery spell from your hand without paying its mana cost."